At least two people were killed in an explosion at a camp for people driven from their homes by the Boko Haram conflict in northeast Nigeria, emergency services on the ground said Friday.
"There was a blast at Malkohi IDP (internally displaced persons) camp in Yola around 11 o'clock this morning (1000 GMT)," Red Cross official Aliyu Maikano said.
There were conflicting reports of the death toll at the camp, one of several in the capital of Adamawa state housing men, women and children who have fled the brutal, six-year campaign by Boko Haram, an armed group which is trying to carve out a state in the country's north based on its fundamentalist version of Islam.
Adamawa state police spokesman Othman Abubakar told Agence-France Presse that two people were killed and seven injured, while the Red Cross' Maikano and the National Emergency Management Agency put the toll at three dead and nine injured.
Suleiman Mohammed, director of response, relief and rehabilitation at the Adamawa State Emergency Management Agency (ADSEMA), said five were killed and 20 injured.
The Adamawa state governor, Jibrilla Bindow, was reported as telling a meeting of northern governors that children were among the dead.
"There were NEMA (National Emergency Management Agency) officials, IDPs and some from the AUN (American University of Nigeria)" among the casualties, said Mohammed.
Lionel Rawlings, head of security at the AUN, which is based in Yola, confirmed student volunteers were injured by flying debris.
"None was in direct contact with the explosion but there was flying shrapnel. We dodged the bullet," he said.
Abubakar and Mohammed both said the blast was caused by an improvised explosive device left by tents in the camp, which is just outside the city to the south and near an army base.
Security had been tight after hundreds of women and children held hostage by Boko Haram were brought to the camp after they were rescued by the military earlier this year.
Armed soldiers manned the gates and carried out checks on vehicles and passengers, AFP reporters witnessed on a visit to the camp in May.
"Our men are there," said Abubakar. "They are trying to find if there are any other explosives."
Yola has been seen as a relative safe haven from the violence and last year its population more than double in size to about 400,000 as those made homeless flocked to the city.
Many of the displaced were housed at state-run camps or stayed with relatives and friends.
Boko Haram has increasingly reverted to guerrilla tactics such as bombing "soft" civilian targets or suicide attacks in the face of an apparent military surge that has regained rebel-held territory.
Nigeria President Muhammadu Buhari, elected earlier this year on a promise of defeating the Boko Haram fighters, on Monday said the military was gaining ground in the counter-insurgency.
He has given his new military high command, appointed in early August, three months to end the conflict, which has left at least 15,000 dead and made more than two million homeless since 2009.
Al Jazeera and Agence-France Presse