REYNOSA, Mexico (AP) - In a ratcheting up of tactics in a long, bloody war, drug cartel gunmen made seven especially brazen assaults on Mexican soldiers in one day this week, throwing up roadblocks near army garrisons and spraying checkpoints with automatic weapons fire.
The apparently coordinated assaults raise the prospect that parts of Mexico could be descending into open warfare between the cartels and the government.
Drug bosses appeared to have little to show for Tuesday's attacks near the Texas border except a body count for their own side: 18 attackers dead, while the military said its own casualties were limited to one soldier with a wounded toe.
But there have been more attacks since, and the battles have shown that gang henchmen are as well armed, if not as well trained, as the soldiers. Armored vehicles, explosive devices and grenade launchers were among the items the military seized.
The attacks are occurring as two cartels are engaged in a violent power struggle of their own. Experts on the drug war say drug lords are trying to get military patrols out of the way of the gangs' increasingly bloody battle for trafficking routes in the northern border states of Nuevo Leon and Tamaulipas.
"There does seem to be a shift in what's permissible to the cartels. The army used to be off limits," said Andrew Selee, director of the Mexico Institute at the Woodrow Wilson Center. "There is an escalation in what the drug trafficking organizations are willing to do, but it's hard to tell if it's a permanent change in strategy."
The battles climaxed Tuesday with seven assaults against army positions that left 18 attackers dead across Nuevo Leon and Tamaulipas.
The cartels, however, do match Mexico's military in firepower: Soldiers confiscated more than 50 assault rifles, 61 grenades and eight homemade explosive devices, as well as grenade launchers and six armored vehicles.
The explosives underscore concerns that drug lords may turn to bombings. E-mails and other intercepted communication indicate that the cartels are seeking explosives for attacks, possibly on buildings or along roadsides.
Gunmen kept up the fight Thursday, blockading roads again in Reynosa. One attacker was killed in a shootout between soldiers and armed men in the city's main Hidalgo Boulevard, according to the state government.
The government has arrested several top drug lords and their lieutenants since President Felipe Calderon deployed troops and federal police across the country more than three years ago to wrest territory from the cartels.