Gunmen ambushed a military patrol in western Mexico, killing two soldiers in a tense state gripped by a standoff between a drug cartel and vigilantes, a prosecutor said Monday.

The attack compounded a tense weekend in Michoacan after self-defense forces seized another town, buses were burned and their most prominent leader was injured in a plane crash.

The soldiers were on patrol Sunday on a road leading to the city of Apatzingan when they shot back at the unidentified assailants, Michoacan's chief prosecutor Marco Vinicio Aguilera Garibay told AFP.

"Two soldiers died in an attack by an armed group whose whereabouts are unknown," he said.

Apatzingan is a bastion of the Knights Templar drug cartel, whose reign of violence in Michoacan prompted civilians to form self-defense forces in several towns almost a year ago.

The state's most prominent vigilante leader, Jose Manuel Mireles, was hurt in a plane crash late Saturday.

The 55-year-old doctor suffered a head injury and dislocated jaw when the small plane made an emergency landing as he returned home from the Jalisco state city of Guadalajara.

A man died and three other people were injured in the crash, which took place hours after vigilantes seized the town of Paracuaro and disarmed a dozen local police officers.

On Sunday, two buses were hijacked and burned on a road leading to Paracuaro, blocking access to the town. Officials say the vigilantes torched the but the militia says it was the work of the Templars.

Mireles, meanwhile, was transferred in a police Black Hawk helicopter to an undisclosed hospital in Mexico City on Sunday for security reasons, federal officials said.

Authorities are investigating the crash but state prosecutors said the plane was forced to land due to a mechanical failure.

Officials said Saturday that Mireles was stable and conscious but there have been no new reports of his health since then.

In a December interview with AFP, Mireles said the civilian militias would continue seizing towns as long as authorities do nothing to protect them from the murders and extortion perpetrated by the Templars.

Another vigilante leader, Hipolito Mora, told AFP on Monday that Mireles' injury would not stop the movement and that Apatzingan, the economic heart of the lime-producing region, remained a target.

"The doctor is a very important person for the movement but there are other people behind it," Mora said.

"(The Templars) are irritated. They don't want the self-defense groups to spread because they had got used to dominating everything," he said.

President Enrique Pena Nieto deployed thousands of troops to Michoacan in May to curb the violence but murders have continued to plague the state, which has become a major security challenge for his administration.

More than 77,000 people have died in drug-related violence across Mexico since 2006.

In Michoacan, the vigilante forces have spread despite state and federal government warnings that their expansion would not be tolerated.

Authorities suspect that the self-defense units are backed by a rival cartel from Jalisco state, a charge the vigilantes deny.

"The situation in Michoacan is getting worse," said Raul Benitez Manaut, a security expert at the National Autonomous University of Mexico. "A more energetic federal intervention, with more troops ... along with social development and education institutions."

Self-defense forces have also formed in the neighboring state of Guerrero, where some 5,000 members and supporters of the movement marked its first anniversary with a march on Sunday in Ayutla de los Libres, the first town to take up arms in January 2013.