| ROSARITO, Mexico
ROSARITO, Mexico Four people believed to be Americans were shot in the head and dumped in a notorious drug-smuggling area in northern Mexico near the California border, Mexican police said on Monday.
Police in the beach town of Rosarito, across the border from San Diego, said they discovered the bodies of three men and a woman on Sunday in an abandoned car in a remote patch of scrubland near the Pacific coast.
Police concluded the victims were U.S. citizens because the vehicle had California license plates, the men appeared to be black, the woman was white and a U.S. driver's license was found in the car, the spokesman said.
Murders have jumped in Mexico this year, the bulk of them linked to a war between rival drug cartels and security forces that has killed some 1,300 people across Mexico since January. But it is unusual for foreigners to be the victims.
"The bodies had been there for at least a week. They were spotted by local people out hunting," a municipal police spokesman said.
The area where the bodies were found is one of many along the border that gangs use to smuggle marijuana and cocaine into the United States.
In Chihuahua state, which borders Texas, gunmen killed senior police officer Jose Martinez as he left his home in the city of Parral on Monday morning, the state attorney general's office said.
Martinez was head of criminal investigations for southern Chihuahua.
"IT'S A WAR"
President Felipe Calderon, who sent out thousands of troops and federal police to battle drug cartels when he took power in December 2006, said on Monday the escalation in violence was reason to press on.
"It's a serious fight, it's a war, and it means assuming the consequences," he told a news conference following talks with visiting German Chancellor Angela Merkel.
"There is no way the Mexican government will give up this fight. Our pledge and decision is to carry on until we rescue Mexico fully from a situation of abuse and crime," he said.
Drug violence killed more than 2,500 people in Mexico last year. Grisly slayings in 2008 include the beheading this month of a man whose head was dumped on top of a car in the northern city of Monterrey.
Half a dozen high-ranking police officers have been killed this month alone.
Violence has spilled over from the rough city of Tijuana into once-quiet Rosarito and its outlying areas as gangs fight over smuggling routes into California.
(Reporting by Lizbeth Diaz in Rosarito, Miguel Angel Gutierrez in Mexico City and Robin Emmott in Monterrey; Writing by Catherine Bremer, editing by Philip Barbara)