Three people were killed in an explosion Friday at a Nigerian camp for people displaced by Islamic extremist attacks, an official said.

Nine people were also wounded by the explosion in a tent in the Malkohi camp in Yola, capital of Adamawa state in northeast Nigeria, said Saad Bello, the National Emergency Management Agency coordinator for the state.

No group claimed responsibility for the blast, but suspicion has fallen on Islamic extremist group Boko Haram.

Boko Haram's uprising, which started in 2009, has caused the deaths of an estimated 20,000 people.

More than 1,000 people have been killed since President Muhammadu Buhari was elected in March with a pledge to wipe out the militants. At least 2.1 million have been driven from their homes by the uprising.

Camps for internally displaced are spread out in Adamawa, Yobe and Borno states, which have been hardest hit by Boko Haram's uprising. The group had seized a large swath of northeastern Nigeria where it declared an Islamic caliphate. A multinational army earlier this year drove the insurgents out of towns and villages, but suicide bombings and village attacks continue.