When vigilantes in northwestern Nigeria's Tungar Kara town prepared to go after an armed gang in a nearby forest last Saturday, residents cheered and prayed for their safe return.

But before they set off on their mission, the town was bombed in an airstrike by the Nigerian Air Force (NAF), which it said targeted the armed gang but residents said killed 15 civilians - members of the vigilante group and other bystanders.

The army and air force have increasingly used aerial assaults against the growing threat in Nigeria's northwest and central region posed by armed criminal gangs, known locally as bandits, which kill villagers and carry out mass kidnappings.

But the campaign is exacting a heavy toll on Nigerian civilians and sapping their support for the military, residents and analysts say.

Salihu Usman, one of the vigilantes tasked with protecting the town from armed gangs, said he was praying when a jet roared in the sky. Then he heard a loud blast and found himself lying injured on the ground.

"Now whenever I see a military plane flying during daytime, I think it is a threat to my life," said Usman, who said his stomach was partly ripped open and has lacerations on his body.

"Bandits kill us and the military bombed us from the sky."

The NAF did not respond to questions from Reuters. In a statement on Monday, the NAF denied it targeted civilians but said it would investigate Saturday's strike on Tungar Kara, a remote town in northwestern Zamfara state.

Haliru Attahiru, a 30-year-old farmer, said he did not believe the airstrike was an accident.

"How do you come to bomb people in the town and not in the forest? The bandits are there in the forest," he told Reuters by phone.

In December, an airstrike killed 10 people in nearby Sokoto state, in an attack the state governor said had mistakenly targeted civilians. The strike continued a pattern of deadly aerial attacks by the military in which civilians have been killed, the subject of a Reuters special report in June 2023.

"If the people discover that they are not saved from the bandits and are fast becoming collateral damage through the air campaigns by the air force, it will affect their support for the military," Oluwole Ojewale, a researcher at the Institute for Security Studies, said.

Usman would not be returning to his vigilante group after his narrow escape. He says he now harbours a distrust for the military and even doubts that the airstrike was a mistake. "I even suspect they collaborated to harm us," he told Reuters.