A series of explosions in the northern-eastern Nigerian town of Monguno has killed an estimated 20 people.
A witness told the AP news agency they were caused by a sack of home-made bombs found at an old Boko Haram camp.
People had gathered to inspect the devices on Tuesday evening when they detonated, he said.
Despite a successful military crackdown on the Islamist militants this year, there have been continued suicide attacks blamed on the militants.
The BBC’s Nigeria correspondent Will Ross says there is no official information about the incident in Monguno, about 135km (83 miles) north-east of the Borno state capital, Maiduguri, or how the devices exploded.
One hospital source said there were close to 20 killed and almost 50 injured, he says.
Eyewitness Haruna Bukar told AP news agency that anti-Boko Haram vigilantes were patrolling the area when they discovered the abandoned militant camp.
They found a bag of metal objects, which they carried to the nearby town of Monguno, where they later exploded, he said.
Our reporter says it seems that while celebrating this discovery at least one of the improvised explosive devices (IEDs) went off killing and injuring people who had gathered around.
This incident highlights the danger that remains even after Boko Haram fighters have been flushed out of an area, he says.
According to Amnesty International, at least 17,000 people, mostly civilians, have been killed since the group launched their violent uprising to impose Islamic rule in 2009.
The group is still holding many women, girls and children captive, including 219 schools girls it kidnapped from a school in Chibok in April last year.
With the help of Niger and Chad, Nigeria’s military has been able to recapture towns and villages taken by the group.
Despite losing territory and retreating to the Sambisa forest, the militants are still active in the north-east and Chad blamed Boko Haram for two suicide attacks in its capital, N’Djamena on Monday.