The MLC are allied to the Ugandans
The United Nations are to send a team to northeastern Democratic Republic of Congo within the next two days to investigate reports of a massacre.
A spokeswoman for the UN mission monitoring the ceasefire in the Congo told the BBC they were trying to get permission from the Lendu group, who control the area where the killings are alleged to have taken place.
On Monday, Jean-Pierre Bemba, head of the Congolese Liberation Movement (MLC), said that hundreds of people had been killed by pro-government soldiers and other militias and called for an investigation.
Last year, the main antagonists in the four-year Congolese war signed a peace deal.
The government of Joseph Kabila, Rwanda, Uganda and the main rebel groups agreed to set up a new power-sharing government.
But fighting has continued in Ituri province near Bunia, featuring a myriad of different groups and shifting alliances.
About 150,000 people have fled the fighting, according to Reuters news agency.
There has been no independent confirmation of the killings.
At the weekend, Thomas Lubanga, head of another rebel group in the area, the Union of Congolese Patriots (UPC), says that 467 civilians were killed in renewed fighting near the town of Bunia.
He also accused Ugandan troops of being involved.
DR CONGO'S WAR
Seven foreign armies
At least 2 million dead
Disease and abuses widespread
This was denied by Ugandan Defence Minister Amama Mbabazi.
Mr Lubanga blamed most of the fighting on the RCD-ML group, led by Mbusa Nyamwisi, who denied that his troops were involved.
They are one of the groups that split from the main Rwandan-backed rebel group, the RCD, to receive backing from Uganda and ally themselves with the MLC.
Ethnic Hemas and Lendus have been fighting for many years over land.
The UPC is largely Hema, according to the UN's Irin news agency.
Last week, UN Secretary General Kofi Annan said he was very worried about the situation in Ituri.
He also criticised the government for putting obstacles in the way of UN officials trying to investigate its alleged links to some of the militias fighting in the area.
MLC fighters have been accused of murder, rape and cannibalism during fighting in Bunia in the past year.