A running series of gun battles caused at least 11 deaths in the northern Mexico border state of Tamauilpas, authorities said Monday.
Officials said the shootouts in the border city of Reynosa and the nearby town of Rio Bravo started late Sunday.
Gunmen hijacked vehicles and used them to block streets, and spread bent nails to puncture tires to facilitate their getaways.
Authorities called in a helicopter to support ground patrols moving to break up the roadblocks.
One group of four gunmen was killed near a gas station after they opened fire on a military patrol, officials said. Three other bodies were discovered at other points around Rio Bravo.
Police found 13 improvised armored vehicles, which are usually light trucks with welded steel plating. Such vehicles are often used by drug gangs in Tamaulipas.
Officers also found six hand grenades, 17 40-mm rifle-launched grenades and about three dozen guns, including a .50-caliber sniper rifle.
The dead included a man apparently killed by assailants after he and a child sought shelter from gunfire in a house on their way to school. The man and child emerged from the house when the shooting died down temporarily, and that is when the man was hit.
Three people also were killed in what appeared to be targeted shootings in the town of Padilla, farther south.
Reynosa is across the border from McAllen, Texas, and has been the scene of turf battles between factions of the Gulf cartel.
In Chihuahua, another northern border state, prosecutors said Monday that the death toll from a shootout in the remote mountain town of Uruachi had risen to seven.
About 100 state police officers were sent to the town after the Friday gunfight, which apparently involved a dispute between rival gunmen.
(Source: AP)