At least five people were killed and thousands suffered power cuts after clashes and reprisals between Mexican vigilantes and members of a drug cartel known as the Knights Templar.
The weekend confrontations in the state of Michoacan followed a daring march by a self-defence force into the city of Apatzingan, the central stronghold of the pseudo-religious Knights Templar cartel.
State Interior Secretary Jaime Mares said soldiers and federal police had taken over security in Apatzingan following the clashes.
Since rising up in February against extortion by the Knights Templar, residents of a half dozen towns that formed self-defence patrols have lived without access to Apatzingan, a commercial and road hub that is home to the region's main hospital and markets.
Self-defence leaders said they finally grew tired of the cartel blocking services and commerce in an attempt to strangle their uprising and showed up on Friday in Apatzingan's outskirts, armed and ready to "liberate" the city.
They were turned back by soldiers who said they couldn't enter with weapons.
A convoy of hundreds of unarmed self-defence patrol members returned on Saturday and successfully entered the city, where they were met by gunfire, presumably from the Knights Templar.
"They attacked us with grenades and with M60 machineguns, judging by the bullet holes in some of our vehicles," self-defence leader Jose Manuel Mireles said Monday.
Mireles said the Knights Templar was apparently outraged by the invasion of their stronghold, and early on Sunday attacked defensive trenches constructed by the self-defence patrols near Apatzingan's outskirts.
Local police said five men were found dead following that attack, but Mireles said self-defence patrol members saw 12 dead cartel gunmen and lost one of their own.
Power cuts and fire bombs
Cartel members were suspected of attacking electrical stations in 14 towns in apparent retaliation, cutting power to about 400,000 people. About a half dozen petrol stations were also attacked.
The Interior Department said in a Sunday statement that fire bombs and several different types of guns were used, but did not identify the attackers.
"It was the Knights Templar who did it, to pressure the government and intimidate them into disarming the self-defence forces," said Hipolito Mora, leader of self-defence forces in the hamlet of La Ruana.
Although the government has said it won't tolerate vigilantes, it has let the self-defence forces operate in most towns.
The control of the Knights Templar group was once so complete that it would have been unthinkable for any rival to enter Apatzingan.
The Knights Templar often travelled in vehicles marked with its symbol, a red cross, and sponsored demonstrations calling for the federal police to leave the city.