British counterterrorism officers arrested several Iranian men over an alleged plot to attack an unspecified target in London, the Metropolitan Police force said Sunday.

Police said five men aged between 29 and 46 were detained on Saturday in various parts of England on suspicion of preparing “a terrorist act.”

Four are Iranian citizens and the nationality of the fifth is still being established.

All the suspects are being questioned at police stations and have not been charged. Police said they are searching several properties in London, Manchester in northwest England and Swindon in western England.

Police said the attack plot targeted a single location that was not being named “for operational reasons.”

Commander Dominic Murphy, head of the force’s Counter Terrorism Command, said police are still working to establish a motive “as well as to identify whether there may be any further risk to the public.”

Separately, three other Iranian men, aged 39, 44 and 55, were arrested in London on suspicion of a national security offense as part of an unrelated investigation, police said.

Home Secretary Yvette Cooper said the arrests were “serious events that demonstrate the ongoing requirement to adapt our response to national security threats.

“The government continues to work with police and intelligence agencies to support all the action and security assessments that are needed to keep the country safe,” she said.

Police have not determined whether the alleged plot is connected to Iran, but Britain’s domestic intelligence service has warned of a growing threat from attackers linked to Tehran.

In October, the head of the MI5 domestic security service, Ken McCallum, said his agents and police have tackled 20 “potentially lethal” plots backed by Iran since 2022, most aimed at Iranians in the U.K. who oppose the country’s authorities.

He said at the time there was there is the risk “of an increase in, or broadening of, Iranian state aggression in the U.K.” if conflicts in the Middle East deepened.

In March 2024, Pouria Zeraati, a presenter at a Farsi-language television station critical of the Iranian government, was stabbed in the leg outside his home in London. Two men were later arrested in Romania and charged over the attack.

The U.K.’s official terror threat level stands at “substantial,” the middle of a five-point scale, meaning an attack is likely.

(AP)