By Mica Rosenberg

MEXICO CITY - Complaints of torture, murder and illegal detention by the Mexican army have jumped as soldiers have been dragged into a long, gruesome battle with powerful drug cartels, Amnesty International said on Tuesday.

Mexico's national human rights commission received some 2,000 accusations of abuse by the military in 2008 and the first six months of 2009, a sharp jump from 367 complaints in 2007 and 182 in 2006, the rights group said in a report.

In one case documented by Amnesty, 31-year-old Saul Becerra was picked up in an army raid at a car wash in Ciudad Juarez, near the U.S.-Mexico border.

His body was found a year later and his death certificate showed he died the day after his detention of a severe brain hemorrhage from blunt-force trauma.

"The cases that we have been able to investigate are truly shocking. But what is more shocking is that we know that this is only the tip of the iceberg," Kerrie Howard, deputy director of Amnesty's Americas program, said in a statement.

President Felipe Calderon has deployed 49,000 soldiers across Mexico to combat the feuding drug cartels who control cocaine trafficking from South America, produce methamphetamines and grow marijuana for U.S. consumers.

The army has failed to curb violence with more than 16,000 people killed in the drug war since Calderon took office in late 2006 and the president risks losing public support for his military-backed crackdown.

Thousands of people protested against the army presence in Ciudad Juarez on Sunday, calling for troops to leave.

Mexico's interior ministry said in a statement it would look seriously at Amnesty's report and that the army was committed to protecting human rights.

Generals in Mexico City deny systematic rights abuses by soldiers and say any troops caught working for the cartels or failing to respect human rights are tried in military courts.

U.S. AID TIED TO RIGHTS

The army has taken on more policing roles because many of Mexico's police forces are working for the drug gangs, and soldiers often clash with local law enforcement.

In March, 25 police officers were detained by the military, held incommunicado for 41 days and tortured to illicit false confessions, the Amnesty report said.

One police officer told human rights investigators how he was beaten for hours until he fainted and was given electric shocks on his feet and genitals.

Other people detained by the army said they were suffocated temporarily with plastic bags or told they would be executed.

The United States has promised Mexico S$1.95 billion in aid to boost Calderon's anti-drug campaign but so far only about 2 percent, or S$36 million, has been spent in Mexico, said a recent report from the U.S. government accountability office.

Fifteen percent of the drug aid can be withheld if there are legitimate complaints of human rights abuses committed by the Mexican army. But U.S. President Barack Obama said on a visit to Mexico earlier this year that the drug traffickers were the biggest violators of human rights.