Mexican president Andrés Manuel López Obrador has called for an investigation after a video emerged that appears to show a Mexican soldier telling his colleagues to kill a survivor of a shootout with suspected cartel gunmen.

The footage, published by El Universal newspaper, shows an incident that the newspaper said came from a shootout in Nuevo Laredo last month, when 12 people who authorities said were drug cartel members were killed.

The video, apparently filmed from a helmet camera, shows a soldier firing a mounted gun from an army truck speeding along a dark highway in Nuevo Laredo, a violent northern city that borders the United States.

The video shows the vehicle coming to a halt near a pick-up truck, where after more shooting a person calls out to hold fire.

“He’s alive,” soldiers shout in the video, pointing to the bed of a pick-up truck used by the alleged gang members.

“Kill him!” someone can be heard yelling, followed by an expletive in Spanish.

Reuters has been unable to verify the contents of the video.

López Obrador said he had asked for an investigation and said it appeared soldiers were ordered to “finish off” a suspect.

He said his government would “not allow this practice.“

The military has been dogged by allegations of extrajudicial killings since former president Felipe Calderon sent the army to bring gangs to heel in 2006.

The struggle has taken a toll on the reputation of the armed forces.

At the time of the incident, the military said there were no survivors requiring medical assistance. According to an official statement afterwards, the gunmen attacked soldiers near the city’s airport.

El Universal previously reported that three kidnapped civilians, with their hands and feet tied, were also among those killed by the soldiers.

The defence ministry has not commented on the video. One ministry official told Reuters the military supports an inquiry.

“The process will proceed under the presumption of innocence,” the official said.