Ciudad Juarez: Gunmen ambushed a police vehicle responding to an emergency call in the violent border city of Ciudad Juarez on Saturday, killing four officers and wounding two bystanders, authorities said.

The officers' vehicle was near an intersection when gunmen drove by and began shooting, said Adrian Sanchez, a public safety department spokesman. The officers died in their car.

It was unclear how many vehicles the gunmen used, and police did not release a motive for the shooting.

Sanchez said one of the two injured bystanders was a 10-year-old girl.

Ciudad Juarez, across the border from El Paso, Texas, has become one of the world's most violent cities as Mexico's drug war escalates. The Sinaloa and Juarez drug cartels are battling for control of the city, and more than 2,000 people have been killed this year so far.

In western Mexico, police in the Pacific resort city of Acapulco said two headless and handless bodies were hung from a freeway overpass in a gruesome display of the growing level of violence and retaliation by cartels.