El Chapo’s cartel tortured rival gang members before hanging their mutilated bodies from a bridge, foreign media reports.
The victims were found in the city of Fresnillo in the north-central Mexican state of Zacatecas on June 19.
Their killers had left them half-naked and placed bags over their heads.
Days earlier, Sinaloa Cartel members interrogated three soldiers from the Jalisco New Generation Cartel [CJNG].
It is believed they were tortured and then tied to the bridge, Infobae reports.
The two gangs have been waging a bloody war for years, and repeatedly clash for control of drug trafficking routes into the US.
The latest killings reportedly formed part of Sinaloa Cartel’s “Operation MZ”.
It was initially announced last October in the state of Nayarit, with the letters referring to leader Ismael “El Mayo” Zambada.
He has taken charge of the cartel since El Chapo’s extradition and imprisonment last year.
In a disturbing video message, several armed men threatened local government officials and warned “heads will roll” in the CJNG territory.
Asked if the message amounted to a declaration of war, Robert Almonte, cartel expert and former US federal marshal, said at the time: “Yes, I believe it does, not only in this state, but in general.”
He added that the name of the operation means it was “at least sanctioned by El Mayo, and it is coming from the top of the Sinaloa Cartel”.
It is likely that “hundreds of foot soldiers” will be involved, along with corrupt law enforcement and military officials.
Last December, seven bodies were found in Zacatecas after another Sinaloa Cartel massacre.
They were left with a note reading: “This is going to happen to everyone who is kidnapping, extorting and collecting fees.”
However, the CJNG has still risen to become the most dominant gang in Mexico in recent years.
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Led by Nemesio “El Mencho” Oseguera Cervantes, a former ally of Chapo, it operates in at least 35 states across Mexico and Puerto Rico.
Last July, authorities estimated the gang oversaw one-third of all drugs being transported from Mexico into the US.
That year, dozens of armed CJNG members shouted Mencho’s name and showed off military-grade weapons along with armoured pickup trucks in disturbing propaganda footage, believed to have been recorded in the state of Jalisco.