Mexican authorities hunting 12-year-old gunman

Mexican authorities are hunting a 12-year-old gunman who has allegedly been used by drug cartels to torture and murder rivals.

The boy, known as "El Ponchis" [The Cloak], has been working for the South Pacific cartel, which has allied itself with rogue ex-government fighters to wage war against the massive La Familia cartel over the drug trade in southwest Mexico.

He is said to work with a group of girls, including his sisters, who often help with disposal of bodies.

The boy reportedly tortures his victims before killing them, and uses a special cutting technique when slitting the throat of a victim to leave their head attached to their body by just a thread.

Videos have surfaced on the internet showing El Ponchis slashing the throat of one enemy and photos are circulating of him posing with various weapons.

The youth tells an unseen questioner that his gang was paid $US3000 ($A3,001) per killing.

"When we don't find the rivals, we kill innocent people, maybe a construction worker or a taxi driver," El Ponchis is heard saying.

Pedro Luis Benitez, the attorney general of central Morelos state, told a local radio station on Friday that police had detained a minor who allegedly worked as a gunman for a drug cartel and were looking for another. He did not say whether the minor who was detained was El Ponchis.

While Benitez did not give the age of the suspects, he implied they were young enough to be playing with toy guns.

"It is easy for them (criminals) to give them a firearm, making it appear as it if were a plastic weapon and that it is a game, when in fact it is not," Benitez said.

President Felipe Calderon, who launched the offensive against cartels in 2006, acknowledged several months ago that "in the most violent areas of the country, there is an unending recruitment of young people without hope, without opportunities."

Suspects under 18 are prosecuted in a separate legal system for youthful offenders for most crime in Mexico. But there are growing calls for both that and the nation's overcrowded adult prison system to be revamped.

Mexico has more than doubled the number of people in federal prisons in the last two years as part of the country's crackdown on drug cartels, the country's top cop said on Friday. While the federal prison system had about 4,500 inmates in 2008, there are now 11,000.