At least 39 people are reported to have been killed in the shoot-out in the municipality of Tanhuato, in the western state of Michoacan on Friday.

The Reuters and AFP news agencies both cited government officials speaking on condition of anonymity who said at least two federal police officers were among those killed. The official who spoke to AFP described the death toll as a "preliminary figure."

If wasn't immediately clear what sparked the fire fight, but it happened in a region where powerful and often violent drug cartels have been active for a number of years.

Tanhuato is not far from the town of Yurecuaro, where mayoral candidate Enrique Hernandez was shot dead at a campaign rally last week.

Hernandez had been a leader of Yurecuaro's vigilante "self-defense force," one of a number of groups that emerged in 2013 to try to drive out the Knights Templar drug cartel after it had been weakened through the arrests of its top figures.

pfd/msh (AFP, Reuters, AP)