Leftist guerrillas firing mortars overran a key army outpost, killing nine soldiers and wounding 15 others, in an attack that indicates the rebels can still mount large-scale operations despite military claims to the contrary.

The army said six guerrillas were killed in the attack early Tuesday morning at El Paraiso, a garrison where an American military adviser was killed in a similar rebel attack in March 1987.In other combat action Tuesday, the military said soldiers attacked rebel positions at Perquin in Morazan province, inflicting 50 casualties on the guerrillas. The number of rebel dead or wounded was not specified. Five soldiers were wounded in the clash, the military said.