At least 11 police officers and two security chiefs have been killed in Mexico's southern Guerrero state, say local media quoting police sources.
They say a security patrol was ambushed by unidentified gunmen in the Coyuca de Benítez municipality, just west of the Pacific resort of Acapulco.
Some of the victims of Monday's attack were handcuffed before being shot dead, El Universal newspaper says.
Guerrero has been plagued by violence related to drug-trafficking.
Various groups in the area battle for control of the lucrative drug routes north along the Pacific corridor.
The region is also a hotspot for the growing of opium poppies and the production of heroin.