At least 12 people were killed and another dozen were wounded in an attack early Sunday on a pre-Christmas party in central Mexico, authorities in the state of Guanajuato said.
The violence occurred in the town of Salvatierra, reportedly at a hacienda, or ranch, that can be rented out for festivities.
"So far 12 people are reported dead," the state's prosecutor's office said on X, the former Twitter.
Twelve others who were wounded have been taken to hospital, according to authorities.
The Tierra Negra foundation, which promotes social projects in the area, said the victims were young people participating in "posadas," religious gatherings that celebrate aspects of the story of Christmas.
A person who was at the party but asked not to be identified for security reasons told AFP that about six men with long guns entered the venue and began circulating among the 100 or so young people gathered at the event.
"We realized they were not invited, and when they were asked who they were, they started shooting," he said.
The victims were "all young acquaintances, admired and very good people. It's a horror what is happening in Salvatierra," Tierra Negra member Carlos Silva wrote on social media.
Three years ago, in the city of some 90,000, authorities discovered unmarked graves with at least 50 bodies.
Guanajuato is one of the most violent states in Mexico, due in large part to the presence and activity of criminal gangs -- including a pair of feuding drug cartels.
"I condemn the unfortunate act of violence that occurred in the community of San Jose del Carmen this morning. We are thoroughly cooperating with the prosecutor's office," Salvatierra Mayor German Cervantes posted on Facebook.
In a separate incident late Saturday about 50 kilometers (31 miles) away from Salvatierra, four men were shot dead in the city of Salamanca, also in Guanajuato, when attackers on motorcycles arrived at a barber shop and opened fire, local officials said.
Similar attacks have been recorded in recent years in Guanajuato, which this year topped the list of states with the most homicides in Mexico, with 3,029 so far, according to official figures.