At least 36 people were killed by extremists in conflict-riddled eastern Congo, the Congolese military said on Thursday. The Allied Democratic Forces, a rebel militia with links to the Islamic State group, killed civilians in Mukondi, a village in North Kivu province 25km SW of Beni in an attack that began late Wednesday, according to survivors. Military forces arrived too late to protect the villagers, according to a local leader who said the ADF fighters left back into the forest with hostages before troops could arrive. Officials from provincial capital Beni toured the stricken village Thursday afternoon, as villagers buried the dead in a mass grave. Conflict has been simmering in eastern Congo for decades as more than 120 armed groups fight for power, influence and resources and some to protect their communities. The ADF has been largely active in North Kivu province but has recently extended its operations into neighbouring Ituri province and to areas near the regional capital, Goma. The ADF rebels are accused by the U.N. and rights groups of targeting, maiming, raping and abducting civilians, including children. Earlier this month the United States offered a reward of up to $5 million for information that could lead to the capture of the group's leader, Seka Musa Baluku. The attack began around 7 p.m. Wednesday when men with guns and machetes stormed the village and started indiscriminately killing people, witnesses told The Associated Press by phone. “The rebels came and they first burned houses. Then everyone who came out of his house was either cut up with machetes or shot dead," said Saddam Patangoli, a resident of Mukondi village who fled the attack and returned to his home the following day. They also abducted many civilians, he said. Some people are blaming the incident on the Congo army's lack of presence in the area. ADF's persistence and evolution in eastern Congo for nearly three decades exposes the extent of the challenge facing the government, say analysts.