The Metropolitan Police carried out searches in Scotland as part of an investigation into national security.
Counter-terrorism police searched a home in East Kilbride amid a probe into spying for Chinese intelligence services.
The address was one of a number of properties including London and Cardiff that were searched on Wednesday.
Officers from Metropolitan Police arrested three men on suspicion of spying for China. The suspects – aged 39, 43 and 68 – were all cuffed south of the border in London and Wales.
They were detained on suspicion of offences under section three of the National Security Act 2023.
Commander Helen Flanagan, head of Counter Terrorism Policing London, said: “We have seen a significant increase in our casework relating to national security in recent years and we continue to work extremely closely with our partners to help keep the country safe and take action to disrupt malign activity where we suspect it.
“Today’s arrests are part of a proactive investigation and while these are serious matters, we do not believe there to be any imminent or direct threat to the public relating to this. Our investigation continues and we thank the public for their ongoing support.”