The US president, Joe Biden, and his top justice department official have welcomed the arrest in Mexico of Néstor Isidro Pérez Salas, known as “El Nini”, allegedly the notorious head of security – and assassination – for the Chapitos wing of the Sinaloa cartel.

The security chief is accused of leaving a trail of murder and torture, including feeding rivals to pet Bengal tigers, and running a security operation known as Los Ninis, “a particularly violent group of security personnel for the Chapitos”, according to the US government, whose members “received military-style training in multiple areas of combat, including urban warfare, special weapons and tactics, and sniper proficiency”.

In a statement, Biden thanked Mexico’s president, Andrés Manuel López Obrador, and the Mexican army and special forces for “effectively capturing” Pérez Salas and expressed “appreciation for the brave men and women of Mexican security forces who undertook this successful operation to apprehend him”.

The US attorney general, Merrick Garland, separately thanked Mexican authorities for capturing the 34-year-old, who provided protection for three sons of the convicted trafficker Joaquín “El Chapo” Guzmán: Iván Guzmán Salazar, Alfredo Guzmán Salazar, and Ovidio Guzmán López, who was apprehended after an intense gun battle and later extradited to the US earlier this year.

Pérez Salas allegedly participated in setting off violence that left 30 people dead, including 10 military personnel.

The US government claims the group, known collectively as Los Chapitos, are responsible for large-scale fentanyl and methamphetamine production and trafficking into the US. In a statement, Garland said Pérez Salas and his security forces “murdered, tortured, and kidnapped rivals, witnesses, and others who opposed the Chapitos”.

Pérez Salas allegedly participated in the torture of a Mexican federal agent in 2017.

According to an indictment unsealed in April, the Ninis would take captured rivals to ranches owned by the Chapitos for execution. “While many of these victims were shot, others were fed, dead or alive, to tigers” belonging to the Chapitos, “who raised and kept tigers as pets”, according to the indictment.

The Ninis are also accused of testing fentanyl on human subjects until they overdose. According to the indictment, the two Ninis leaders – Pérez Salas and Jorge Figueroa Benitez – “experimented on a woman they were supposed to shoot” and “injected her repeatedly with a lower potency of fentanyl until she overdosed and died”.

The indictment also alleges that 28 members and associates of the Mexican Sinaloa cartel, including El Chapo’s three sons, and placed on them responsibility for importing fentanyl precursor chemicals from China.

Fentanyl and methamphetamine smuggled by the Chapitos into the US from Mexico has led to hundreds of thousands of deaths, according to US prosecutors. The Chapitos have said through lawyers they are being “scapegoated”.

But the remarks by both Biden and Garland thank the Mexican president for Pérez Sala’s arrest, and coming a week after Biden made an agreement “in principle” with China’s president, Xi Jinping, to curb the export of fentanyl precursors to Mexico, underscores that the diplomatic emphasis being placed on the issue.

US authorities are now seeking the extradition of Pérez Salas, who had a $3m bounty on his head and was arrested at a walled property in the Sinaloa state capital of Culiacán. Mike Vigil, former head of international operations for the US Drug Enforcement Administration, told the Associated Press that El Nini “was a complete psychopath”, adding: “Taking him out of commission is a good thing for Mexico.”