Three men were gunned down following an argument with a woman at a bar in Ocotepec, a city in the central Mexican state of Morelos, prosecutors said.
The woman made a telephone call after the argument and told the people on the other end, "come over here," the Morelos Attorney General's Office said in a statement, citing eyewitness accounts.
Several men armed with assault rifles and wearing hoods drove up to the bar, went inside and opened fire, the AG's office said.
One of the dead men was found outside the bar along with a message threatening several gangs.
The second body was found inside the bar and the third man, who worked as a waiter at the establishment, died at a hospital.
The gunmen wounded 16 people, including four who are listed in serious condition at hospitals, the AG's office said.
Morelos has been the scene in recent years of turf wars involving rival drug cartels.
Earlier this month, the dismembered bodies of two men were found buried in trash bags at a house in Temixco, a city in Morelos.
Two assault rifles - an AR-15 and an AK-47 - a .38-caliber revolver, four ammunition clips for an AK-47 and ammunition were found buried near the bodies.
The Familia Michoacana, Los Zetas, Pacifico Sur, Sinaloa and Gulf cartels all operate in the state, officials say.
About 50,000 people have died in Mexico's drug war since December 2006, when President Felipe Calderon declared war on the country's powerful cartels, sending soldiers into the streets to fight criminals. EFE