May 25 (Reuters) – Mexico on Saturday extradited to the United States Nestor Isidro Perez Salas, or “El Nini,” who headed security for the sons of ex-Sinaloa Cartel kingpin Joaquin “El Chapo” Guzman, in one of the highest profile extraditions in recent years.

Seen by U.S. anti-narcotics agents as being among the most ruthless Mexican drug figures, Perez was detained in November by the Mexican National Guard in the northwestern city of Culiacan, the Sinaloa Cartel’s heartland.

“We allege El Nini was one of the Sinaloa Cartel’s lead sicarios, or assassins, and was responsible for the murder, torture, and kidnapping of rivals and witnesses who threatened the cartel’s criminal drug trafficking enterprise,” U.S. Attorney General Merrick Garland said in a statement.

Perez is accused by the United States of leading the “Ninis,” a violent group of security personnel working for Ivan Archivaldo Guzman and other sons of jailed former Sinaloa kingpin, El Chapo.

Ivan and three other sons of El Chapo, who emerged from their father’s shadow to head a powerful faction of the Sinaloa Cartel known as “Los Chapitos,” have become some of the most wanted targets for U.S. law enforcement. The U.S. Drug Enforcement Administration (DEA) alleges Los Chapitos are the biggest fentanyl traffickers to the United States.

Perez, meanwhile, is one of the highest-profile extraditions during the presidency of Andres Manuel Lopez Obrador, who assumed power in December 2018.

In a sign of Perez’s importance to authorities on both sides of the border, the DEA chief Anne Milgram sent an internal memo to agency staff praising his extradition.

Milgram, in the memo reviewed by Reuters, described Perez’s Ninis outfit as a violent group that receives military-style training and is tasked with “kidnapping, torturing and killing anyone who oppose the Chapitos or anyone who endangers the Chapitos’ fentanyl operation.”

U.S. courts have indicted Perez on a slew of charges in relation to his alleged role at the helm of the Chapitos’ security apparatus, including cocaine and methamphetamine trafficking conspiracy, possession of machine guns and witness retaliation.

Reporting by Brendan O’Brien in Chicago and Drazen Jorgic in Mexico City Editing by Chris Reese