The ADF militia killed 57 civilians in displacement camps in the eastern DR Congo on May 31, the United Nations said Friday, voicing outrage at the gun and machete assaults.

UNHCR, the UN Refugee Agency, said the deadly attacks by the Allied Democratic Forces group had forced some 5,800 people to flee multiple displacement sites in the eastern Democratic Republic of Congo's Ituri province.

"On May 31, ADF simultaneously attacked displacement sites and villages near the towns of Boga and Tchabi, killing 57 civilians --including seven children -- who were shot and attacked with machetes," UNHCR spokesman Babar Baloch told reporters in Geneva.

"Several others were left wounded and 25 people were abducted, while over 70 shelters and stores were set on fire. In Boga town alone, 31 women, children and men were killed.

"Bereaved family members told UNHCR partners that many of their relatives were burnt alive in their houses.

"UNHCR is outraged by this latest in a series of atrocities committed by armed groups in eastern DRC."

The agency called for security in the region to be scaled up urgently to protect civilians, many of whom have been attacked and forced to flee multiple times.

The ADF is the deadliest of scores of armed militias that roam the mineral-rich eastern DRC.

It is historically a Ugandan Islamist group that has holed up in eastern DRC since 1995. 

In March, the United States said the ADF was linked to the Islamic State jihadist group.

Baloch said that thousands had fled Boga to various nearby locations "with virtually nothing but the clothes they were wearing".

He said that while most had been welcomed in by impoverished host families, some were sleeping out in the open, while others have sought refuge in already overcrowded churches.

Baloch added that one of UNHCR's humanitarian partner organisations had its offices looted, leaving thousands short of aid.

The UNHCR said more than five million people had been uprooted by insecurity and violence in the DRC, with 1.7 million displaced in Ituri alone.

The agency said its financial appeal of $204.8 million for DRC in 2021 was only 18 percent funded.