Multiple explosions hit a refugee camp in northeastern Nigeria, killing at least four people and injuring 18 others. The camp offers shelter to people fleeing Islamist militants Boko Haram.

The explosions hit the Muna Garage camp area around 4.30am (3.30am GMT), the police commissioner of the city of Maiduguri Damian Chukwu told Reuters on 22 March.

Chukwu added that two of the explosions happened at the camp, which shelters internally displaced people fleeing the Islamist militants, who seek to establish an Islamic caliphate in northeastern Nigeria.

The number of the explosions is contested, as the coordinator of the Muna camp Tijjani Lumani told AFP there were four explosions – suicide bombs – inside the camp.

"The explosions triggered fires which burned down many tents," he added.

Unicef Nigeria wrote a statement on Twitter expressing "deep concern for people impacted by explosions overnight". According to The Office for the Coordination of Humanitarian Affairs in Nigeria (OCHA), the camp hosts "tens of thousands" of internally displaced people.

This is the latest in a string of attacks in the Maiduguri area, one of the worst affected by the violence, where bombings on Sunday 19 March killed four people.

A man claiming to be Boko Haram's leader appeared in a video released on 17 March claiming responsibility for bombings in the city.

Who are Nigeria's Boko Haram terrorists?

Boko Haram, which has renamed itself Iswap, fights against Western influence in Nigeria and aims to impose its version of Sharia law throughout occupied territories.

The group launches attacks in Nigeria and neighbouring countries in a bid to take control of more territory. Three Nigerian states − Adamawa, Borno and Yobe − have been under a state of emergency since May 2013.

Boko Haram has killed more than 20,000 people since 2009 and was deemed the world's deadliest terror group, surpassing Islamic State in November 2015. Nigeria has also become the world's third-most terrorised country as a result of the group's violent insurgency.