(Adds Calderon quote in last paragraphs)

By Lizbeth Diaz

TIJUANA, Mexico, Dec 4 (Reuters) - Gunmen killed the police chief of a Mexican city bordering California on Tuesday by shooting him 50 times in an apparent revenge attack after police found a drug-smuggling tunnel under the border.

Gunmen broke into the house of Tecate police chief Juan Soriano in the early morning and shot him repeatedly in the face and torso as he slept in bed with his wife, an official at the Baja California state attorney general's office told Reuters. His wife was not hit.

The killing of Soriano, who had started his job only last week, appeared to be an act of revenge against Mexican police, who on Monday discovered a tunnel nearly a mile (1.6 km) long running into California from Tecate near the Pacific coast after a tip from the U.S. Border Patrol.

"As soon as Soriano made public the discovery of the tunnel, he went home and, hours later, they executed him in his bedroom," said the official, who requested anonymity.

Police also found two tonnes of marijuana in a vehicle near the tunnel, which ran from an abandoned warehouse close to the Tecate crossing point into a rural area of Southern California, and was one of the longest ever discovered along the U.S.-Mexico border.

The Mexican government says its deployment this year of 25,000 troops and federal police across Mexico is halting drug violence between warring cartels fighting for dominance of smuggling routes to the United States.

But violence has continued in Baja California, where more than 300 people have been killed this year.

Drug violence has killed 2,350 people so far this year and hundreds of police have died in gangland-style murders.

President Felipe Calderon, who launched the army crackdown within days of taking office in December, said on Tuesday that he did not expect to win the war on cartels during his six-year term.

"It's a very long war. It's going to take us a very long time," Calderon told local radio. Asked whether he could overpower the powerful trafficking gangs during his term, Calderon replied: "Of course not. It's a permanent battle." (Additional reporting by Luis Rojas, editing by Doina Chiacu)

AlertNet news is provided by