Mexican officials say 33 people have been killed in the space of 24 hours in Mexico's industrial capital, Monterrey.
Security officials in the northern state of Nuevo Leon, where Monterrey is located, said most of those killed had links to the country's drug cartels.
But two of the victims were identified as bodyguards of the governor of Nuevo Leon, Rodrigo Medina.
Police said a threatening message addressed to Mr Medina had been found next to the bodies.
Mr Medina said the threats would not stop his determination to beat organised crime.
A spokesman for the Nuevo Leon Security Council, Jorge Domene Zambrano, said the killings were almost all connected to a deadly battle for control of the region between rival drug cartels.
"Only five have links to the authorities - the two bodyguards, and three guards from Cadereyta prison," he explained.
According to the authorities, five presumed gang members were killed in a battle with the army and 10 people died in a confrontation between rival gangs.
The bodies of the remaining victims were found dumped in various parts of the city and, in some cases, hanged from bridges.
The state is the stronghold of the Zetas, thought to be one of Mexico's most violent drug cartels.
They are engaged in a deadly battle with the Gulf, Sinaloa, and La Familia gangs.