The shootout occurred when soldiers were patrolling Miguel Aleman municipality on the border with the US, the office of Tamaulipas’s spokesman for security said on social media.

It said members of the Secretariat of National Defense (Sedena) “were attacked by armed civilians who were hiding in the bush” at around 2pm local time.

The clash left “12 assailants dead”, and soldiers seized 12 guns and an array of ammunition, it added.

State government sources confirmed to AFP that the 12 attackers, alleged members of a drug cartel, were killed in the incident, during which the military also used drones and a helicopter.

Situated on the US border, Tamaulipas is one of the states hardest hit by violence linked to organised crime.

It is the site of constant clashes between gangs fighting over lucrative drug trafficking routes.

Four US citizens, two of whom later died, were snatched at gunpoint after crossing the border into Tamaulipas state in a minivan in March last year.

Mexico has registered more than 420,000 murders and 110,000 disappearances – most attributed to criminal groups – since the launch of a controversial military anti-drug offensive in 2006.