At least 12 inmates at a Guatemalan youth prison have been killed in the latest fighting between two rival street gangs.

Police and witnesses say members of the Mara Salvatrucha gang carrying assault rifles raided the prison and attacked inmates from a rival gang, Mara 18.

At least 10 prisoners were wounded in the attack, which took place late Monday at a jail outside Guatemala City. News reports say at least two of those killed were decapitated.

Earlier Monday, three prisoners were killed in gang violence at another prison in the city of Puerto Barrios.

Gang violence has become a recurring problem in Guatemalan prisons. In August, 35 inmates were killed as gangs battled for control of several different jails.