Mexican police found nine decapitated bodies on Sunday in a city near the tourist resort of Acapulco, and at least some of the victims might have been soldiers who were battling against powerful drug gangs.

The bodies of the men, which were marked with signs of torture, were left on the side of a highway, while their heads were stuffed in a plastic bag found outside a shopping center, police in the state of Guerrero told Reuters.

Local media reported that nine soldiers were abducted on Saturday as they left a regional military base near the city of Chilpancingo, about an hour north of Acapulco. An army spokesperson could not confirm that the victims were soldiers.

Mexico's President Felipe Calderon has deployed tens of thousands of soldiers and federal police since 2006 to take on cartels that move cocaine and other drugs into the United States.

A note left with the severed heads warned that more authorities would be decapitated, the state police said. The state police chief said some of the victims were soldiers, Reforma newspaper reported.

Calderon's offensive has helped fuel a major increase in drug violence. More than 5,300 have died so far this year, over twice as many as in 2007, according to the attorney general's office.