Northern Ireland police say they are questioning four suspected members of an Irish Republican Army faction after stopping a car in Catholic west Belfast and finding a loaded assault rifle.

The 29-year-old driver was arrested at the scene Thursday night and three other men aged 27, 29 and 46 were arrested in raids on homes overnight. All four were being questioned Friday at the police interrogation center west of Belfast.

Several IRA factions opposed to Northern Ireland's 1998 peace accord and Catholic-Protestant unity government continue to plot gun-and-bomb attacks in the British territory. But police have thwarted many attacks by using electronic surveillance and informer tipoffs.

Earlier this week, seven suspected IRA members faced terrorism charges based on conversations secretly recorded by the British spy agency MI5.