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TIJUANA, Mexico (Reuters) - Police found six charred bodies, one still on fire, dumped on a street in the northern Mexican city of Tijuana on Monday, in the latest brutal killing on the U.S.-Mexico border.


A police spokesman said drug gangs were believed to be behind the attack.

"Some of the victims were shot dead or beaten. It's not clear if any were burned alive," said the spokesman, who declined to be quoted by name.

Tijuana is one of the most gruesome fronts in Mexico's three-way war between rival drug cartels and security forces, as Mexico's most-wanted man Joaquin "Shorty" Guzman tries to wrestle control of smuggling routes into California from the city's long dominant Arellano Felix cartel.

Following two months of relative quiet in Tijuana, across the border from San Diego, California, drug murders and kidnappings are rising again, police say. At least 14 people have been killed in drug violence since early Sunday.

Shootouts between drug gangs have killed some 300 people in the city this year, making up a chunk of the more than 1,700 drug murder victims across Mexico since the start of 2008.

Monday's burnt bodies were found two days after suspected drug hitmen in southern Mexico dumped a severed human head inside a black bag in the tourist city of Oaxaca, along with a threatening message for Mexican law enforcement, the state public prosecutor's office said.

President Felipe Calderon has sent thousands of troops to Tijuana and across the country to fight warring drug gangs but the military operations have failed to curb the violence. Killings have increased this year to unprecedented levels.

U.S. and Mexican anti-drug officials say higher street prices show fewer narcotics are getting through to the United States and that increased drug violence is a sign that cartels are weakening.

(Reporting by Lizbeth Diaz; editing by David Wiessler)