At least 19 people have been killed in an armed attack in the state of Michoacán, in western Mexico, officials say.

Gunmen swooped down on an illegal cockfighting pit in the community of Las Tinajas and opened fire, local media report.

The motive behind the attack is not yet clear but a number of criminal gangs operate in the region.

Bloody attacks on gatherings of rivals have become increasingly common.

In recent months, gunmen in various regions of Mexico have targeted funerals and wakes as well as bars and clubs in their attempt to take out as many of their rivals at one time as they can.

Forensic experts said all the victims in Las Tinajas - 16 men and three women - had been killed by gunshots. A number of people have also been injured.

Witnesses said the gunmen opened fire indiscriminately before fleeing in various cars. In a recording tweeted by local news site Red Michoacán, dozens of shots can be heard ringing out.

Soldiers have been deployed to try and hunt the attackers down.

The area around Las Tinajas is disputed by a number of gangs which engage in the smuggling of stolen petrol and the illegal tapping of petrol pipes owned by the state-run oil company.