Four people have been arrested as part of a counter-terrorism investigation relating to Iran, the Metropolitan Police has said.
Police arrested one Iranian and three dual British-Iranian nationals on suspicion of assisting a foreign intelligence service.
The investigation relates to the suspected surveillance of locations and individuals linked to Jewish communities in London, the Met said.
Commander Helen Flanagan, head of Counter Terrorism Policing London, said the arrests were part of "a long-running investigation and part of our ongoing work to disrupt malign activity where we suspect it".
She added : "We understand the public may be concerned, in particular the Jewish community, and as always, I would ask them to remain vigilant and if they see or hear anything that concerns them, then to contact us."
