Six police were killed Wednesday in a clash with gunmen in the northeastern Mexican state of Tamaulipas, authorities said.
The battle took place shortly after 3:00 a.m. near the town of Padilla on the highway linking Ciudad Victoria, the state capital, with Matamoros, just across the border from Brownsville, Texas.
The victims were identified only as three members of the Tamaulipas Rural Police and three municipal traffic officers.
They were killed less than 24 hours after state Public Safety Secretary Ives Soberon resigned to make way for Antonio Garza Garcia, erstwhile federal police commissioner in the western state of Michoacan.
Tamaulipas has been battered this year by a turf war between the Gulf drug cartel and the rival Los Zetas outfit, leaving hundreds dead.
The Zetas are blamed for the massacre of 72 undocumented migrants late last month at a Tamaulipas ranch not far from the U.S. border.