The sons of imprisoned drug kingpin Joaquin "El Chapo" Guzman are suspected of launching an ambush on a military convoy in northern Mexico which killed five soldiers and injured 10 others.
State and military officials said on Saturday that some 60 gunmen freed drug suspect Julio Oscar Ortiz Vega, also known as "El Kevin", in Culiacan city in Sinaloa state, as he was being escorted by soldiers to a hospital in an ambulance. Vega had been wounded in an earlier gunfight.
General Alfonso Duarte, a regional commander, told reporters that Guzman's sons were "very probably" responsible for the attack.
Duarte said the convoy was ambushed by armed men hurling grenades which caused two vehicles to burst into flames.
The suspect was "being transferred to Culiacan for immediate medical attention ... but unfortunately this group acts in a premeditated, cowardly, treacherous way, using firearms and grenades," Duarte said.
President Enrique Pena Nieto vowed on Twitter to bring those responsible to justice.
"El Chapo" was re-captured earlier this year following his brazen escape from a maximum security prison in July 2015.
That escape was the second for "El Chapo" in 15 years and a major embarrassment for Mexico's President Enrique Pena Nieto.
The notorious drug lord was first captured in 1993 in Guatemala, but he escaped from a prison in western Mexico in 2001 by hiding in a laundry cart.
He is currently in prison in Ciudad Juarez, a northern city on the US border.
