The death toll during a shootout on Thursday between Mexican army and a group of suspected gangsters in northern state Nuevo Leon has risen to 27, authorities said.

Earlier reports said that 25 had died in the fighting. The clash was in the municipality of General Trevino, close to state capital Monterrey.

A Defense Ministry spokesman told local media that all the dead were criminal suspects. However, officials so far have not been able to identify to which gang they belonged.

The clash started when soldiers were fired upon close to camp.

Defense Ministry staff consulted by Xinhua were not immediately able to confirm details of the incident.

Forensic Medical Service staff are now at the scene recovering corpses, while staff from state prosecutors and police are gathering other evidence in order to begin an investigation.

Nuevo Leon has seen growing violence in recent months due to clashes between Los Zetas and the Gulf Cartel. The two groupings were former allies who fell out and are now competing in the region's most lucrative illegal business: smuggling drugs into Mexico's northern neighbor the United States.