The bloodshed occurred during a Christmas posada, traditional Mexican celebration, in the community of San Jose del Carmen, the Guanajuato Attorney General's Office was quoted as saying by Xinhua news agency, adding that an investigation is underway.

According to initial reports from the municipal government, a group of armed attackers arrived unexpectedly and opened fire at posada participants, the majority of them young people, leaving 12 dead and 10 injured.

The injured people were rushed to hospital for treatment.

In recent years, violence has increased in the region due to the dispute between criminal groups seeking control, Xinhua reported.