Leftist rebels stormed a maximum-security prison in the Salvadoran capital, wounding three guards and freeing more than 100 inmates, including 13 political prisoners, police said.

The rebels, using mortars, small arms and grenades, fought guards at the Mariona Prison for 20 minutes and blew holes in the south wall through which the prisoners escaped.

Police, reinforced by government troops, armored vehicles and helicopters, sealed off the area and launched a search for the rebels. A prison official said 104 inmates had escaped -- 13 political prisoners and 91 convicts.

Late Thursday, guerrillas machine-gunned a truck whose driver ignored rebel warnings to stay off the roads, killing a woman passenger and wounding three other civilians, the Salvadoran Army said.

The attack occurred along the highway leading to Jucuapa, 55 miles southeast of the capital.

The Army said the rebels were retreating from a battle with U.S.-backed government troops when they ambushed the truck with submachine guns.

The guerrillas have said that their highway sabotage campaign, in its third day, is aimed at destroying El Salvador's fragile economy.

Heavy fighting broke out Thursday between rebels and Army troops near Chinameca, in San Miguel province 46 miles southeast of San Salvador, an Army officer said.