The attack on the Mexican military convoy on Friday (30 September) that left five soldiers dead was probably carried out by the sons of drug kingpin Joaquin "El Chapo" Guzman, an official said.

The assault happened on the outskirts of Culiacan in the northern state of Sinaloa when the convoy was escorting an injured drugs suspect in an ambulance.

According to reports, the assault, which involved grenades and assault rifles, was carried out to free the captured suspect, Julio Oscar Ortiz Vega, also called "El Kevin".

Around 60 men attacked the military group and succeeded in their motive. They also took the ambulance and set two military trucks ablaze.

"Up this point we are not certain about this group, but it is very probable that it was the sons of Chapo," local military commander Gen Alfonso Duarte said.

"These groups acted with cowardice, in a premeditated manner, and carried out the attack with weapons, with grenades," while the soldiers had only automatic weapons, Duarte added.

Vega was held in El Chapo's hometown of Badiraguato in Sinaloa. He was allegedly involved in a conflict over control of drug production. According to authorities, Guzman's brother, Aureliano Guzman Loera, also known as "El Guano", is struggling for control of drug production against Alfredo Beltran, a leader of the rival Beltran Leyva cartel. However, it remained unclear Vega was on which side.

Mexican President Enrique Pena Nieto has announced to punish those involved in the attack and said that justice will be provided to the victims.