A federal takeover is under way in an area of western Mexico known as Tierra Caliente, or Hot Land, where heavily armed vigilantes have taken up a fight against a local drug cartel.
Mexico's interior minister Miguel Angel Osorio Chong said Monday that government troops would take over security in the region with support from authorities in Michoacan state, where the area is located.
The announcement in the state capital, Morelia, followed a string of firefights between the vigilantes and alleged members of the so-called Knights Templar cartel.
The interior minister called on the vigilante groups to return to their activities as citizens and leave security in the hands of the institutions. But the leader of one vigilante group, Estanislao Beltran, said they will not disarm.
Masked vigilantes took power in more than a dozen rural communities last year in Michoacan state, arguing authorities were failing to stop drug violence.
Opponents and critics claim the vigilante groups are backed by a rival cartel — a charge the vigilantes deny.
Until now, government forces had not interfered with the groups even as they spread into more and more communities.
On Sunday, hundreds of vigilantes seized control of the town of Nueva Italia, reportedly disarming police.
The civilian militias say they have now surrounded the Knights Templar cartel's stronghold of Apatzingan, raising fears of a bloody confrontation.
The unrest is posing a major security challenge for Mexican President Enrique Peña Nieto who took office a little more than a year ago, pledging to reduce drug violence. More than 75,000 people have been killed in the nation's drug war since Peña Nieto's predecessor, Felipe Calderón, launched his crackdown on the drug gangs in 2006.
Following the interior minister's announcement, the Mexican attorney general's office said it was sending 11 helicopters and 70 investigators and officers to Michoacan state.