MEXICO CITY (Reuters) - A suspected lieutenant of Mexico's most wanted drug lord captured this week was likely responsible for at least 350 murders, the government said on Thursday.
Mario Nunez, aka "El Mayito" or "M-10," was believed to be the operations chief of Joaquin "Shorty" Guzman in Chihuahua, a state bordering the United States which has been wracked by drug-related violence over the past few years.
"This person (Nunez) is related to, and believed to be responsible for, the murder of more than 350 people recovered from 23 hidden mass graves," said government national security spokesman Eduardo Sanchez.
Known in Mexico as "El Chapo," Guzman heads the Sinaloa Cartel, which is widely regarded as the country's most powerful drug-running organisation.
Chihuahua is home to Ciudad Juarez, a sprawling border metropolis that became notorious in recent years as one of the most violent cities in the world. Police arrested Nunez, a former policeman in the city, in Ciudad Juarez on Tuesday.
Guzman's cartel has suffered few reverses over the past year. Many of the government's heaviest blows have landed against the Gulf Cartel and the Zetas, a group founded by ex-soldiers deemed to be the most brutal of the gangs.
Over the last few weeks the government has captured a suspected boss of the Gulf Cartel, in addition to the leader of the Zetas, Miguel Angel Trevino.
Going after cartel bosses, which critics say only serves to splinter the gangs and increase the violence, was a hallmark of former President Felipe Calderon's drug strategy.
During Calderon's 2006-2012 administration, which sought to bring the gangs to heel with a military crackdown, about 70,000 people died in drug-related violence.
President Enrique Pena Nieto, who took office in December, was critical of Calderon's strategy.
However, earlier this week Pena Nieto watered down one of his flagship security measures, a militarized police force that was meant to replace the army on the streets.
The force is set to be much smaller than originally anticipated, raising questions about whether Pena Nieto will be able to fulfil his pledge to scale back the presence of the military from states which are still dogged by gang violence.
The overall death toll has fallen, according to the government, but drug-related violence has still claimed about 1,000 lives a month since Pena Nieto took office.
Reporting by Lizbeth Diaz and Gabriel Stargardter; Writing by Gabriel Stargardter; Editing by Dave Graham and Richard Chang