Mexican armed forces will take over security in a large swath of a western state where shootouts between vigilante groups and drug traffickers erupted over the weekend, a top official has announced.

Miguel Angel Osorio Chong, the Mexican interior secretary, said federal forces with support from Michoacán state police would patrol an area in the state known as Tierra Caliente, the home base of the Knights Templar drug cartel. "Be certain we will contain the violence in Michoacán," Osorio Chong said.

He gave no details on what federal agencies would be involved or give numbers on planned forces. Some federal police and troops have been sent to the region in recent months because of the unrest but have generally not intervened.

The federal attorney general's office said later in a statement it had sent 11 helicopters and 70 federal investigators and officers to help return law and order to the state.

Osorio Chong made his announcement after a meeting called by the Michoacán state governor, Fausto Vallejo, following a weekend of firefights between drug traffickers and some of the vigilante groups that have sprung up by the dozens over the past year to confront the gangs.

Congressman Ernesto Nunez of the Green party, who was at the meeting in the state capital of Morelia, said the federal government was looking to have members of the self-defence groups join police departments. "Those who they see really have the [police] vocation, those who really love their communities, will be invited to join the police," Nunez said.

Estanislao Beltran, a leader of a vigilante group, rejected the idea of giving up their guns or becoming police officers. "If we give up our weapons without any of the drug cartel leaders having been detained, we are putting our families in danger because they will come and kill everyone, including the dogs," Beltran said.

He said none of the members of the vigilante groups aspired to be police officers. "What we are doing is fighting for the freedom of our families," he said.

No clashes were reported in the Tierra Caliente region on Monday but almost every store was closed in Apatzingan, the biggest city in the area. There were few people on the street and little police presence.

Shopkeepers said they were afraid to open after gunmen believed to be working for the Knights Templar cartel threw firebombs at several of the city's businesses and city hall over the weekend. A report circulated among worried townspeople that the cartel had threatened to burn down the city of 100,000 people, said Javier Cortes, spokesman for the diocese of Apatzingan. "They are saying they want to leave Apatzingan in ashes," Cortes said. "This will end when the self-defence groups enter the city."

On Sunday hundreds of members of one vigilante group entered another town, Nueva Italia, and disarmed the local police as part of what they say is a campaign to free communities from the control of the Knights Templar. Shooting broke out almost immediately in and around the town square. One injury was reported.

Opponents and critics contend the vigilantes are backed by a rival cartel. The groups deny that.

Osorio Chong said federal authorities would go after anyone acting outside the law and called on self-defence group members to return to their villages.

The federal government has said the civilian vigilante groups are operating outside the law. They carry high-calibre weapons that Mexico only allows for military use. But government forces have not moved against the groups and in some cases have appeared to be working in concert with them.

Rumors circulate that some self-defence groups have been infiltrated by the New Generation cartel, which is reportedly fighting a turf war with the Knights Templar in Michoacán, a rich farming state that is a major producer of limes, avocados and mangoes.

Some in the region say members of the Knights Templar have also tried to use self-defence groups as cover for illegal activities.