At least 11 people have been killed in northeastern Nigeria in an attack on a security convoy that was taking people displaced by an armed uprising back to their homes, police and security sources said.

The ISIL (ISIS) group, to which a breakaway faction of Nigerian armed group Boko Haram pledged allegiance in 2016, said on its Amaq website that 30 police officers and soldiers were killed in the attack on Friday on a road leading to the strategic fishing town of Baga in Borno state.

In a statement on Saturday, Borno state police said eight police officers and three members of a government-approved militia were killed, and 13 people were wounded in the attack about noon (11:00 GMT) on Friday.

Two soldiers, a police officer and a member of the government-approved militia – all speaking anonymously because they were not authorised to speak to journalists – told Reuters news agency at least four soldiers were also killed.

Armed groups have forced more than two million people to flee their homes since 2009 when Boko Haram began an armed uprising aimed at creating a state adhering to a strict interpretation of Islamic law. Some 30,000 people have been killed in the conflict.

The convoy was taking people back to Baga at the start of an initiative by authorities in Borno to relocate displaced people to their homes. Borno is the birthplace of the armed uprising and the state worst hit by the conflict.

Most of the displaced have been housed into squalid camps where they depend on food handouts from international charities.

Unnamed security sources told AFP news agency that Borno Governor Babagana Umara Zulum was part of the convoy but was unhurt in the attack.

In July, Zulum’s convoy came under attack from ISIL’s West Africa Province (ISWAP) outside Baga, forcing him to cancel his trip to the town.

ISWAP has become a dominant force in the region in recent years. The group has recently intensified attacks on military and civilian targets.