At least 20 people have been killed and several others wounded in a mass shooting in central Mexico, authorities have said, in one of the deadliest attacks in recent years, Aljazeera reported.

The authorities did not immediately release a motive for the attack on Sunday evening that targeted a gathering in the town of Las Tinajas in Michoacan state. Local media reports said gunmen stormed a cockfighting pit and shot at the attendees.

It was a massacre of one group by another,” President Andres Manuel Lopez Obrador told a news conference, expressing his regret at the deaths. He blamed criminal gangs for the shooting and said a team was dispatched to investigate the crime.

Officials said those killed included 17 men and three women, according to Aljazeera.

Michoacan and neighbouring Guanajuato state have seen years of violenceamid ongoing turf wars between rival gangs.

Last month, an attack during a wake in Michoacan, believed to be the result of a gang dispute, was reported to have killed up to 17 people.

That attack was believed to be motivated by “revenge” by one cell of the Jalisco New Generation Cartel against another, deputy security minister Ricardo Mejia said. However, the government said it was unable to confirm the death toll because no bodies were found. DNA samples of 11 possible victims were collected at the site, Aljazeera reported.

Michoacan is also the world’s biggest avocado-producing region. Threats against a plant inspector from the United States who worked there last month prompted Washington to suspend Mexican exports of the fruit for more than a week.