Three men have been arrested on suspicion of assisting Russia’s intelligence service, the Metropolitan Police said.
The men, aged 44, 45 and 48, have been arrested as part of an investigation into alleged offences under the National Security Act.
It comes as detectives are working to clamp down on the increasing number of “proxies” who are being recruited by foreign intelligence services, the force said.
They were detained under section 3 of the National Security Act.
The men were arrested at addresses in west and central London on Thursday and are currently in custody at a London police station.
Searches are being carried out at these addresses as well as another address in west London, the force said.
Commander Dominic Murphy, head of Counter Terrorism Policing London, said: “We’re seeing an increasing number of who we would describe as ‘proxies’ being recruited by foreign intelligence services, and these arrests are directly related to our ongoing to efforts to disrupt this type of activity.
“Anyone who might be contacted by and tempted into carrying out criminal activity on behalf of a foreign state here in the UK should think again.
“This kind of activity will be investigated and anyone found to be involved can expect to be prosecuted, and there are potentially very serious consequences for those who are convicted.”
