The decapitated bodies of four men were hung from a bridge Sunday in this central Mexican city besieged by fighting between two drug lords.?

Relatives and friends gather around the coffin of Edelmiro Cavazos, mayor of the tourist town of Santiago, prior to his funeral at a cemetery downtown in the municipality of Santiago, some 30 km (18.6 miles) from Monterrey, August 19, 2010. [Agencies]

A gang led by kingpin Hector Beltran Leyva took responsibility for the killings in a message left with the bodies, the attorney general's office of Mexico state said in a statement.

The beheaded and mutilated bodies were hung by their feet early Sunday from the bridge in Cuernavaca, a popular weekend getaway for Mexico City residents.?

Cuernavaca has become a battleground for control of the Beltran Leyva cartel since its leader, Arturo Beltran Leyva, was killed there in a December shootout with marines.

Mexican authorities say the cartel split between a faction led by Hector Beltran Leyva, brother of Arturo, and another led by Edgar Valdez Villareal, a US-born kingpin known as "the Barbie."

The message left with the bodies threatened: "This is what will happen to all those who support the traitor Edgar Valdez Villareal"

Authorities said the four men had been kidnapped days earlier. The family of one of the men reported the abduction to police.

In western Mexico, police found the body of a US citizen inside a car along the highway between the Pacific resorts of Acapulco and Zihuatanejo.

A report from Guerrero state police said the man was shot to death and had identification indicating he was from Georgia.

The US Embassy could not be reached to confirm the man's identity.

Police said they had no suspects and had not determined a motive.

Guerrero state has been wracked by drug-gang violence, including the strife within the Beltran Leyva cartel. There have also been a series of deadly carjackings this year along highways in the state.

Mexico has seen unprecedented gang violence since President Felipe Calderon stepped up the fight against drug trafficking when he took office in December 2006, deploying thousands of troops and federal police to cartel strongholds.

Since then, more than 28,000 people have been killed in violence tied to Mexico's drug war.