Three arrested in Essex on suspicion of spying for Russia
All three have been bailed while the investigation continues.
Two men, aged 41 and 46, and a 35-year-old woman have been arrested in Essex on suspicion of spying for Russia.
The Metropolitan Police said the trio were arrested at two separate addresses in Grays on suspicion of assisting a foreign intelligence service and taken to a police station in London.
The Met added: "The country to which the allegations relate is Russia."
Commander Dominic Murphy, head of the Counter Terrorism Command, said: "Through our recent national security casework, we're seeing an increasing number of who we would describe as 'proxies' being recruited by foreign intelligence services.
"Indeed, two young British men are awaiting sentencing after they were recruited by the Wagner Group - effectively the Russian state - to carry out an arson at Ukrainian-linked warehouse.
"They are facing potentially lengthy custodial sentences, although, to be clear, today's arrests are in no way connected to that investigation."
All three have been bailed while the investigation continues.
Scotland Yard said it would not disclose the nationalities of those involved.