At least one assassin with a silenced pistol slipped into a guarded hospital room Friday and killed a Moslem suspected in a fatal car bombing, police reported.

They identified the dead man as Mahmoud Ahmed, a 25-year-old Lebanese.Authorities arrested him after a car bomb exploded Sept. 28 at a Syrian army checkpoint on the coastal highway south of Beirut. Five people were killed and 21 wounded, included five Syrian soldiers.

Ahmed was hit in the stomach by shrapnel and was undergoing treatment at the American University Hospital in Moslem west Beirut, police said. They said two plainclothes Syrian agents had guarded him in the eighth-floor room around the clock.

"We do not know how the assassin or assassins managed to slip into the guarded room and shoot him," said a police spokesman.