British police say they have arrested four young men in London on suspicion of plotting terrorist acts in the U.K.

The Metropolitan Police says the men aged 18, 24, 25 and 27 were arrested Wednesday at addresses in east London under the Terrorism Act on suspicion of “the commission, preparation or instigation of acts of terrorism.”

The police force says the arrests are linked to activity in the U.K., but has not revealed details of the alleged plot.

The force says officers are searching five homes and a business in east London as part of the investigation, which is led by counterterrorism police and the domestic intelligence agency, MI5.

British officials have set the threat level from international terrorism at “severe,” indicating an attack is highly likely.

(AP)