LONDON (AP) — British police have arrested four men on suspicion of plotting terrorist attacks.

The arrests were made Tuesday morning by the North East Counter Terrorism Unit. The men were arrested at their homes in Sheffield and Chesterfield in northern England.

Police say the men are being questioned and four residential properties are being searched.

The men were not identified. They range in age from 22 to 41.

They have not been charged.

Police asked local residents to "remain alert but not alarmed."

The official terrorist threat level for Britain is "severe," indicating an attack is considered highly likely.