Armed attackers shot their way into a bar in the city of Torreon, killing eight people and injuring another 19, according to media reports on Sunday.
Ten of the injured are in critical condition, officials said.
The attackers first attacked the bar from the outside early Saturday morning, then opened fire on customers. Two of the victims were security guards.
In other weekend violence, the bodies of four beheaded victims were found in Durango. Drug gangs have increasingly used dismemberment to intimidate local officials and residents.
In Baja California, six people were killed. Sinaloa and Nuevo each saw one killing.
Since December 2006, an estimated 18,000 people have been killed in Mexico's drug wars. When he took office that year, President Felipe Calderon declared war on the drug cartels, using federal police.