Six men aged between 25 and 40 were shot by a heavily-armed assailant who opened fire in a bar in the town center called Tornado, the prosecutor for Coahuila state said.
Earlier the same night, two men were killed in a separate attack in another bar called Futuro, he said.
News of the attacks spread quickly on social media, prompting other bars to eject customers and close down early.
Three bars had already been shot up earlier this week in Torreon, leaving five people dead.
Authorities tie the attacks to drug gang violence, which surged over the weekend, with at least 26 people killed in separate attacks from Friday to Saturday, most in the northern state of Chihuahua, which borders the US.
Police in the western state of Jalisco said seven additional bodies with gunshot wounds were found on the border with neighboring Michoacan state on Sunday morning – again organized criminal gangs were presumed responsible.
At least 70,000 people have died in drug-related violence since 2006, when troops were deployed to battle drug cartels, according to the new government, which took over in December.
New President Enrique Pena Nieto has pledged to reduce the country’s crime rate as he battles the powerful cartels.