MAIDUGURI, Nigeria — Vigilantes on Monday torched the home of a senior politician they accuse of supporting Islamic militants in northeast Nigeria, witnesses said.

The arson came as soldiers acting under a state of emergency killed some 40 men accused of belonging to the extremist Boko Haram group on the outskirts of Maiduguri city, according to a soldier who said he participated in the fighting. The soldier requested his name not be used because he is not authorized to speak to reporters.

The arson was the first indication that the vigilantes, who have been arresting alleged extremists and handing them over to the military, could be getting out of control.

Members of the party of the targeted politician and party chairman Mala Othman said opponents used the vigilantes "to settle cheap political scores" in Maiduguri. Neighbors said soldiers smuggled Othman out of the house before it was invaded by scores of young men who set it ablaze.

Soldiers have been guarding the property since 2011, when Othman said he was receiving death threats from Boko Haram. Residents spoke on condition of anonymity, for fear of reprisals.

On Saturday, joint task force spokesman Lt. Col. Sagir Musa told reporters that they were monitoring the vigilantes' actions to ensure they act within the law.

Nigeria's President Goodluck Jonathan in May declared a state of emergency, saying the extremists had taken control of some towns and many villages in the northeast. The insurgency poses the greatest security threat in years to Africa's biggest oil producer and its most populous nation. Boko Haram preaches that Western education, religion and medicine is forbidden.

Some 2,000 people have been killed since 2010.

The military says a joint task force of soldiers, police, customs and immigration officials has the situation under control. But they appear to have chased the militants into mountains dotted with caves, from which they emerge to attack towns and villages.