UK arrests three on suspicion of Russia-related spying

Those addresses and one other were currently being searched, the Metropolitan Police said, adding that counter-terrorism police were leading the investigation.

"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," said Dominic Murphy, Head of the Counter-Terrorism Policing London.

"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."