At least 25 people were killed in an early Sunday attack in eastern Congo carried out by a militant group linked to the Islamic State, according to a rights group based in Ituri province.

The attack was attributed to the Allied Democratic Force, or ADF, and the rights group said it took place around 4 a.m. The dead included 15 men who were burned alive in a house and seven people who were shot in the village of Apakulu in Irumu territory of Ituri province.

The rights group also said three other people were killed in the Walese Vonkutu administrative area.

Christophe Munyanderu, president of the Convention for the Respect of Human Rights, said: “This tragedy occurred around 4 a.m. and claimed the lives of at least 25 people. This incursion by the ADF is a true massacre.”

There was no immediate statement from the ADF.

The eastern region of Congo has seen multiple attacks in recent months by armed groups, including the ADF and the Rwanda-backed M23 rebel group.

The ADF operates in the border region between Uganda and Congo and has killed civilians, the AP report said. The group grew out of an insurgency against Ugandan President Yoweri Museveni’s rule and was pushed into Congo after Ugandan military assaults, according to the report.

The report also said that last July, the ADF carried out a series of attacks that killed more than 100 people. It said Ugandan and Congolese armed forces have been conducting joint operations against the group.

The AP story was updated to correct the group’s name to Allied Democratic Force.