TEGUCIGALPA- Nine inmates were killed and three wounded in fighting in a prison in Honduras, police in the Central American nation said on Friday.

The violence erupted during a confrontation between rival groups using knives and guns at the penitentiary in the northwestern city of San Pedro Sula, a police spokesman said.

The incident on Friday was the worst so far this year in the overstretched Honduran penal system, which was built for around 5,000 inmates but houses more than 12,000.

In a separate incident on Friday in the city, which has been ravaged by turf wars between drug gangs, six people were killed and three wounded in a shootout at the international airport.

Honduras has the highest homicide rate of any country worldwide, according to a global study published this month by the United Nations.