A Mexican drug detainee has confessed to dissolving the bodies of 300 rivals with corrosive chemicals near the US border, in a shocking claim even by the standards of Mexico's brutal drug war.

Santiago Meza, known as "The Stew Maker," told journalists he did away with bodies in industrial drums in this border village outside the violent city of Tijuana.

More than 700 people died in Tijuana last year as rival gangs battled for control of the city's lucrative drug trade. Many others are missing and believed dead after being abducted.

The suspect, who was paraded before journalists by the army yesterday, said he was paid $600 a week by a breakaway faction of the Arellano Felix cartel to dispose of slain rivals with caustic soda, a highly corrosive substance.

"They brought me the bodies and I just got rid of them," Meza said at a construction site where he claimed to have dissolved 300 corpses last year.

A high-ranking army officer told Reuters he believed Meza, who was arrested with three other people on Thursday, was telling the truth. The bodies took 24 hours to dissolve but left some remains which were dumped in a nearby pit, Meza said.

Police have previously recovered human remains burned with acid in and around the city.

The spiraling violence of Mexico's drug war has cast a pall over the country and presents a huge challenge to President Felipe Calderon, who has deployed thousands of troops to crush the cartels.

The drug war claimed 5,700 lives across Mexico last year, more than double the number of victims in 2007.