MEXICO CITY (Reuters) - Seven decapitated bodies that had been chopped into pieces and burnt were left on a highway in western Mexico on Saturday in a region where rival drug gangs are waging a bloody dispute.

The bodies were found in plastic bags in the cargo bed of a burnt-out pick-up truck in the state of Michoacan near the town of Venustiano Carranza and the border of Jalisco state, the Michoacan attorney general's office said in a statement.

The killings had all the hallmarks of a drug gang attack, a local official said on condition that he was not identified.

Seventeen bodies were found last Sunday in the same region across the border in Jalisco. The area is disputed by drug gangs, including the cult-like Knights Templar gang that dominates trafficking in Michoacan and the Jalisco New Generation cartel.

The truck had been reported stolen earlier this month in the city of Uruapan, a stronghold of the Knights Templar, the statement said. The state of the human remains would complicate the identification of the victims.

Turf wars between the gangs and their clashes with security forces have killed more than 55,000 people since late 2006 during the rule of outgoing President Felipe Calderon, who launched a war against traffickers upon taking office.

More than 8,000 of the corpses left across Mexico since 2006 have not been identified, according to the National Human Rights Commission, a government-run body.

Police found 18 dismembered bodies in May in the same region, near Lake Chapala, a site popular with foreign tourists and American retirees.

(Reporting by Michael O'Boyle; Editing by Jackie Frank)