TIJUANA, Mexico, March 4 (Reuters) - Five youths were tortured, sprayed with bullets and dumped in an empty lot on Tuesday in the Mexican border city of Tijuana, where the army is battling a spike in killings by powerful drug cartels.

The bodies were handcuffed and riddled with dozens of bullets, police said, in one of the bloodiest drug-related murders in Mexico so far this year.

"We think this is another message to discourage major blows to organized crime," a spokesman for Baja California state's security ministry said.

The bodies were found a day after soldiers battled drug traffickers in a five-hour shootout in the border city, just south of San Diego, California. The gun battle killed one police officer and one suspected gang member.

President Felipe Calderon has sent thousands of troops and federal police to Tijuana and other cities in Baja California, Mexico's most violent state, to fight cartels and clean up corrupt police as part of a nationwide drug gang crackdown.

More than 2,500 people were killed in drug violence in Mexico last year and more than 300 have died so far this year as cartels smuggling cocaine, methamphetamine and marijuana fight each other for control of routes to the United States.

One of the victims found on Tuesday was a 16-year-old female. The rest were males between the ages of 17 and 22, authorities said.

Tijuana has suffered a spike in violence in recent weeks, with drug hitmen pinning messages on bodies that warn against Calderon's army-backed operation.

In January, gunmen and more than 100 police and soldiers fought a three-hour battle outside a Tijuana kindergarten. (Reporting by Lizbeth Diaz, writing Cyntia Barrera Diaz)

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