Satellite images reviewed by BBC Verify have shown a major oil slick spreading across the Kerch Strait that separates Russia from annexed Crimea, a month after two oil tankers were badly damaged in the Black Sea.

Oil has leaked into the strait from two ships which ran into trouble during bad weather on 15 December. Volgoneft-239 ran aground following the storm, while Volgoneft-212 sank.

​​Up to 5,000 tonnes of oil has now leaked, and media reports and official statements analysed by BBC Verify suggest the spill has spread across the Black Sea and the Sea of Azov.

A senior Russian scientist called the spill the country’s worst “environmental catastrophe” of the 21st Century.

“This is the first time fuel oil has been spilled in such quantities,” Viktor Danilov-Danilyan – the head of science at the Russian Academy of Sciences (RAS) – said in a 17 January interview with a Russian newspaper.

Russian scientists said in December that this spill could be more than twice the size of a similar disaster in the strait in 2007, which saw up to 1,600 tonnes of heavy oil leak into the sea. Ukraine’s ministry of ecology has estimated that the clear up from the latest spill could cost the Russian state up to $14bn (£11.4bn).

Paul Johnston, a scientist at Greenpeace Research Laboratories, said “there’s always an element of uncertainty around oil spills”, but a lack of timely information has heightened this uncertainty further.

“I’m not entirely optimistic we’ll ever know the full extent of the problem,” he added.

Satellite images reviewed by BBC Verify on 10 January – the most recent available high-resolution photos – showed a massive oil slick running through the strait, measuring at least 25km (15 miles) long. A second, smaller slick measuring around 5.7km (3.5 miles) long is also visible.

Mr Danilov-Danilyan said that oil could “by late January reach Odesa” in southern Ukraine and “one cannot rule out” it travelling as far as the coasts of Romania, Bulgaria and Turkey.

In a statement to BBC Verify, a spokesperson for Greenpeace said the group estimated that oil from the spill now covered an area totalling up to 400 sq km.

The spill appears to have moved quickly after the initial incident. On 24 December, satellite images reviewed by BBC Verify showed oil accumulating on a beach in Anapa – some 40 miles from the strait.

BBC Verify has analysed reports in Russian media, statements from officials and Greenpeace releases from this month that talk about oil being found or cleared up on various beaches.

The reports suggest that the oil has now spread as far north as the occupied city of Berdyansk in Ukraine and as far south-west as Lake Donuzlav on the Crimean Peninsula, which Russian illegally annexed in 2014.

The leak involves heavy M100-grade fuel oil that solidifies at a temperature of 25 degrees Celsius.

A Greenpeace spokesperson told the BBC that M100 doesn’t stay on the water’s surface for long. Once underwater, it is “technically impossible to neutralise”, and can take decades to be biodegraded by marine micro-organisms.

Footage recorded by the Russian NGO The Earth Touches Everyone and included below appeared to show large amounts of heavy oil accumulating on the seabed.

Some experts have warned that the leak has heavily impacted marine life in the region. Footage authenticated by BBC Verify has shown birds covered in oil.

It is not known exactly how many animals have been harmed by the spill.

Overall, Russian officials say about 6,000 birds have been delivered to “rehabilitation centres” on the Russian mainland, but it is unclear how many of them will survive. A local bird sanctuary in Stavropol territory said of 1,051 birds affected by the oil spill that have been delivered to them only about 17% have survived.

Greenpeace told BBC Verify that the final number of dead birds could be far higher, citing the 12,000-13,000 killed by the 2007 spill in the strait.

A dolphin rehabilitation centre in Russia’s Krasnodar Territory told Interfax news agency that around 70 dead dolphins have been discovered on the shores following the latest oil spill.

“This is a horrific blow to the ecosystem,” Mr Danilov-Danilyan told Russia media. He predicted the death of “tens of thousands of birds, many dolphins, [and] big losses in the coastal flora and fauna”.

“Practically nothing, other than microorganisms that feed on fuel oil and break it up, can live in that sort of environment, even in salt water. The removal of 200,000–500,000 tonnes, at least, of contaminated soil too will not go without consequences, and will certainly lead to a reshaping of the coast,” he said.

Dmitry Lisitsyn, Executive Fellow at Yale University’s School of the Environment, told BBC Verify that under Russian safety regulations these types of tankers are barred from leaving rivers in winter.

“Those ships are not intended for high waves, they are very long with a shallow draught,” he said.

Questions have also been raised about the seaworthiness of the vessels, which are both over 50 years old, according to Marine Traffic.

Footage released by Russian authorities showed the bow of one tanker completely broken off during the incident, with streaks of oil visible in the water. The captains of both vessels have been arrested and criminal investigations have been opened into the incident.

Ukrainian activists have accused the ships of being part of Russia’s so-called shadow oil fleet. Moscow has been accused of using the so-called ghost fleet of tankers, which are often poorly maintained and lack proper insurance, to move oil and circumvent sanctions, though analysts the BBC has spoken to could not confirm the claims.

Experts say the long-term fallout from the spill may not be limited to just Russia.

“In general, Russia has suffered more than any other country so far from the Kerch Strait accident,” Dmitry Markin of Greenpeace said.

“However, the majority of the leaked fuel oil is still in the sea. Therefore, the long-term consequences for the occupied territories of Ukraine may be no less severe.”

Graphics by Erwan Rivault.

Julia Ramadan was terrified – the war between Israel and Hezbollah was escalating and she’d had a nightmare that her family home was being bombed. When she sent her brother a panicked voice note from her apartment in Beirut, he encouraged her to join him in Ain El Delb, a sleepy village in southern Lebanon.

“It’s safe here,” he reassured her. “Come stay with us until things calm down.”

Earlier that month, Israel intensified air campaigns against Hezbollah in Lebanon, in response to escalating rocket attacks by the Iran-backed armed group which had killed civilians, and displaced tens of thousands more from homes in northern Israel.

Ashraf was confident their family’s apartment block would be a haven, so Julia joined him. But the next day, on 29 September, it was subject to this conflict’s deadliest single Israeli attack. Struck by Israeli missiles, the entire six-storey building collapsed, killing 73 people.

The Israel Defense Forces (IDF) says the building was targeted because it was a Hezbollah “terrorist command centre” and it “eliminated” a Hezbollah commander. It added that “the overwhelming majority” of those killed in the strike were “confirmed to be terror operatives”.

But a BBC Eye investigation verified the identity of 68 of the 73 people killed in the attack and uncovered evidence suggesting just six were linked to Hezbollah’s military wing. None of those we identified appeared to hold a senior rank. The BBC’s World Service also found that the other 62 were civilians – 23 of them children.

Among the dead were babies only a few months old, like Nouh Kobeissi in apartment -2B. In apartment -1C, school teacher Abeer Hallak was killed alongside her husband and three sons. Three floors above, Amal Hakawati died along with three generations of her family – her husband, children and two granddaughters.

Ashraf and Julia had always been close, sharing everything with each other. “She was like a black box, holding all my secrets,” he says.

On the afternoon of 29 September, the siblings had just returned home from handing out food to families who had fled the fighting. Hundreds of thousands of people in Lebanon had been displaced by the war.

Ashraf was in the shower, and Julia was sitting in the living room with their father, helping him upload a video to social media. Their mother, Janan, was in the kitchen, clearing up.

Then, without warning, they heard a deafening bang. The entire building shook, and a massive cloud of dust and smoke poured into their apartment.

“I shouted, ‘Julia! Julia!,’” says Ashraf.

“She replied, ‘I’m here.’

“I looked at my dad, who was struggling to get up from the sofa because of an existing injury to his leg, and saw my mother running toward the front door.”

Julia’s nightmare was playing out in real life.

“Julia was hyperventilating, crying so hard on the sofa. I was trying to calm her down and told her we needed to get out. Then, there was another attack.”

Video footage of the strike, shared online and verified by the BBC, reveals four Israeli missiles flying through the air towards the building. Seconds later, the block collapses.

Ashraf, along with many others, was trapped under the rubble. He began calling out, but the only voice he could hear was that of his father, who told him he could still hear Julia and that she was alive. Neither of them could hear Ashraf’s mother.

Ashraf sent a voice note to friends in the neighbourhood to alert them. The next few hours were agonising. He could hear rescuers sifting through the debris – and residents wailing as they discovered loved ones dead. “I just kept thinking, please, God, not Julia. I can’t live this life without Julia.”

Ashraf was finally pulled from the rubble hours later, with only minor injuries.

He discovered his mother had been rescued but died in hospital. Julia had suffocated under the rubble. His father later told him Julia’s last words were calls for her brother.

In November, a ceasefire deal was agreed between Israel and Hezbollah with the aim of ending the conflict. The deal gives a 60-day deadline for Israeli forces to withdraw from southern Lebanon and for Hezbollah to withdraw its forces and weapons north of the Litani River. As this 26 January deadline approaches, we sought to find out more about the deadliest single Israeli attack on Lebanon in years.

In the apartment below Julia and Ashraf’s, Hawraa and Ali Fares had been hosting family members displaced by the war. Among them was Hawraa’s sister Batoul, who, like Julia, had arrived the previous day – with her husband and two young children. They had fled intense bombardment near the Lebanon-Israel border, in areas where Hezbollah has a strong presence.

“We hesitated about where to go,” says Batoul. “And then I told my husband, ‘Let’s go to Ain El Delb. My sister said their building was safe and that they couldn’t hear any bombing nearby.’”

Batoul’s husband Mohammed Fares was killed in the Ain El Delb attack. A pillar fell on Batoul and her children. She says no-one responded to her calls for help. She finally managed to lift it alone, but her four-year-old daughter Hawraa had been fatally crushed. Miraculously, her baby Malak survived.

Three floors below Batoul lived Denise and Moheyaldeen Al-Baba. That Sunday, Denise had invited her brother Hisham over for lunch.

The impact of the strike was brutal, says Hisham.

“The second missile slammed me to the floor… the entire wall fell on top of me.”

He spent seven hours under the rubble.

“I heard a voice far away. People talking. Screams and… ‘Cover her. Remove her. Lift the stone. He’s still alive. It’s a child. Lift this child.’ I mean… Oh my God. I thought to myself, I’m the last one deep underground. No-one will know about me. I will die here.”

When Hisham was finally rescued, he found his niece’s fiance waiting to hear if she was alive. He lied to him and told him she was fine. They found her body three days later.

Hisham lost four members of his family – his sister, brother-in-law and their two children. He told us he had lost his faith and no longer believes in God.

To find out more about who died, we have analysed Lebanese Health Ministry data, videos, social media posts, as well as speaking to survivors of the attack.

We particularly wanted to interrogate the IDF’s response to media – immediately following the attack – that the apartment block had been a Hezbollah command centre. We asked the IDF multiple times what constituted a command centre, but it did not give clarification.

So we began sifting through social media tributes, gravesites, public health records and videos of funerals to determine whether those killed in the attack had any military affiliation with Hezbollah.

We could only find evidence that six of the 68 dead we identified were connected to Hezbollah’s military wing.

Hezbollah memorial photos for the six men use the label “Mujahid”, meaning “fighter”. Senior figures, by contrast, are referred to as “Qaid”, meaning “commander” – and we found no such labels used by the group to describe those killed.

We asked the IDF whether the six Hezbollah fighters we identified were the intended targets of the strike. It did not respond to this question.

One of the Hezbollah fighters we identified was Batoul’s husband, Mohammed Fares. Batoul told us that her husband, like many other men in southern Lebanon, was a reservist for the group, though she added that he had never been paid by Hezbollah, held a formal rank, or participated in combat.

Israel sees Hezbollah as one of its main threats and the group is designated a terrorist organisation by Israel, many Western governments and Gulf Arab states.

But alongside its large, well-armed military wing, Hezbollah is also an influential political party, holding seats in Lebanese parliament. In many parts of the country it is woven into the social fabric, providing a network of social services.

In response to our investigation, the IDF stated: “The IDF’s strikes on military targets are subject to relevant provisions of international law, including taking feasible precautions, and are carried out after an assessment that the expected collateral damage and civilian casualties are not excessive in relation to the military advantage expected from the strike.”

It had earlier also told the BBC it had executed “evacuation procedures” for the strike on Ain El Delb, but everyone we spoke to said they had received no warning.

UN experts have raised concerns about the proportionality and necessity of Israeli air strikes on residential buildings in densely populated areas in Lebanon.

This pattern of targeting entire buildings – resulting in significant civilian casualties – has been a recurring feature of Israel’s latest conflict with Hezbollah, which began when the group escalated rocket attacks in response to Israel’s war in Gaza.

Between October 2023 and November 2024, Lebanese authorities say more than 3,960 people were killed in Lebanon by Israeli forces, many of them civilians. Over the same time period, Israeli authorities say at least 47 civilians were killed by Hezbollah rockets fired from southern Lebanon. At least 80 Israeli soldiers were also killed fighting in southern Lebanon or as a result of rocket attacks on northern Israel.

The missile strike in Ain El Delb is the deadliest Israeli attack on a building in Lebanon for at least 18 years.

The village remains haunted by its impact. When we visited, more than a month after the strike, a father continued to visit the site every day, hoping for news of his 11-year-old son, whose body had yet to be found.

Ashraf Ramadan, too, returns to sift through the rubble, searching for what remains of the memories his family built over the two decades they lived there.

He shows me the door of his wardrobe, still adorned with pictures of footballers and pop stars he once admired. Then, he pulls a teddy bear from the debris and tells me it was always on his bed.

“Nothing I find here will make up for the people we lost,” he says.

Additional reporting by Scarlett Barter and Jake Tacchi