British counterterrorism officers arrested several Iranian men over an alleged plan to attack an undisclosed location in London, the London Metropolitan Police announced Sunday.

Five men between the ages of 29 and 46 were taken into custody on Saturday in various parts of England on suspicion of preparing a terrorist act.

Four of the men are Iranian citizens, while investigators are still working to determine the nationality of the fifth.

In a separate investigation, three other Iranian men, aged 39, 44 and 55, were arrested in London on suspicion of a national security offense.

All the suspects are being questioned at police stations but have not yet been charged. (Getty Images)

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.

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

Police said the attack plot targeted a single location, which the agency said is not being revealed “for operational reasons.” (Getty Images)

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

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

The Associated Press contributed to this report.