Clashes between Islamist sect Boko Haram and government-backed civilian vigilantes killed 18 people in Nigeria's northeastern state of Borno, survivors said on Monday, as President Goodluck Jonathan struggles to contain regional violence.
Boko Haram, which wants to impose Islamic law in northern Nigeria, is linked to more than 160 deaths last month and is considered the biggest security threat to Africa's top oil-exporting country.
The dead in Sunday's attack in Benisheik village were five Boko Haram militants and 13 members of a civilian vigilante group, according to the survivors.
Nigeria's government has supported newly-formed vigilante groups as interim security forces as it awaits the arrival of further troops in Borno, one of three states where a state of emergency was declared in May.
The vigilantes and their families have become targets of Boko Haram and scores have been killed in revenge attacks.
"We had received information early in the day on Saturday that the Boko Haram would attack. To this end we were ready for them," said Modu Abuwar, leader of the vigilante group, who was receiving treatment in a hospital in Borno's capital Maiduguri.
"But they outwitted us by climbing trees during the night and started shooting at us early on Sunday, killing 13 of our members and injuring 18," he added.
Abuwar and his colleagues said they killed five members of Boko Haram using their machetes and clubs.
Sunday's attack occurred days after the military said it had killed 50 insurgents further north.