Gunmen suspected to be from the Boko Haram Islamist sect stormed two villages in northeast Nigeria, killing 10 people, after a botched attempt by local vigilantes to arrest some of the militants.
The attack by Boko Haram, which seeks to establish a strictly Islamic state in religiously-mixed Nigeria, occurred on Sunday after vigilante youths tried to approach a militant hideout in Konduga, in remote Borno state.
"The insurgents fled their hideout and, on their way, ambushed our colleagues, killed three of them and invaded Kawuri and Fori," said Ahmed Kyari, a surviving vigilante.
He said the militants shot dead another seven villagers and burned 20 houses to the ground.
Boko Haram's four-year-old insurgency still poses the most serious security threat to Africa's leading oil- and gas-producing state, despite an all-out military offensive against it ordered by President Goodluck Jonathan in May.
Pro-government vigilante activism by angry youth groups has helped the state to capture hundreds of Boko Haram suspects, but the rebels have retaliated with major attacks on civilians.
Boko Haram militants disguised as soldiers killed 19 people at a checkpoint on Sunday, mostly by slitting their throats, witnesses said.
Government forces have also been accused of committing atrocities, with Amnesty International last week reporting that hundreds of Boko Haram suspects were dying in captivity. The military says such abuses are rare.