Three people have been arrested on suspicion of spying on behalf of Russia, the Metropolitan Police has said.
A 41-year-old man and a 35-year-old woman were arrested at an address in Grays, Essex, the force said. A 46-year-old man was arrested at a separate address in the same area.
All three were arrested on suspicion of assisting a foreign intelligence service, contrary to section 3 of the National Security Act (NSA) 2023 and they were taken to a police station in London.
The Met said the country to which the allegations relate is Russia.
Officers carried out searches at the two addresses in Essex and all three people have since been released on police bail with conditions, while the investigation remains ongoing, the Met said.
Cdr Dominic Murphy, head of the Met’s Counter Terrorism Command, said the Met had seen an increasing number of people in the UK being recruited by foreign intelligence services.
He added: “But 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.”
