The authorities in Mexico say eleven people have been killed in a gunfight between the security forces and guerrillas in the southwestern state of Guerrero.

Officials say the fighting broke out after members of the left-wing Popular Revolutionary Army, or EPR, took refuge in a schoolhouse.

Troops detained more than twenty rebels.

It's the worst incidence of violence involving the EPR since it emerged in southern Mexico in 1996, vowing to fight for social justice for Mexico's poor.

The BBC correspondent in Mexico says the guerrillas accuse the government of carrying out an campaign of violence to silence political opponents in the state.