The head of United Nations peacekeeping operations, Jean-Marie Guehenno, has warned that there could be a bloodbath in the town of Bunia, in north-eastern Democratic Republic of the Congo, unless decisive action is taken.
He, along with some African leaders, wants the United Nations Security Council to send extra peacekeeping troops to the area around Bunia, where brutal ethnic fighting continues.
Why is there so much bloodshed in Bunia?
The area around Bunia has a dangerous cocktail of ethnic rivalry, natural resources and foreign soldiers.
Ethnic Hemas and Lendus have a long-standing land dispute, which has been fanned by both Ugandan and Rwandan troops.
The lucrative Kilo Moto gold mines are in the Ituri district which surrounds Bunia, while Canadian firm Heritage Oil Corporation is exploring for oil in the region, according to the United Nations Irin news service.
Why are the Hemas and the Lendus such bitter enemies?
The Lendus are farmers, while the Hemas are both farmers and livestock-rearers.
As in many parts of Africa, farmers and pastoralists clash over land use in Ituri.
But observers say their disputes were worsened by foreign intervention, from colonial times and especially since the Ugandans and Rwandans arrived.
The Lendus are the majority in Ituri but some accuse former colonial power Belgium of favouring the Hemas.
Many Lendus are employed by the more affluent Hemas.
As far back as 2001, a researcher for the lobby group Human Rights Watch said: "The two groups are now identifying with the Hutu-Tutsi categories that figured in the Rwandan genocide.
"The Lendu are now thinking of themselves as kin to the Hutu, while the Hema are identifying with the Tutsi."
How are the foreign armies involved?
Uganda and Rwanda sent troops into DR Congo together in 1998 but they have since fallen out, backing rival rebel groups and militias across the country.
The Hema Union of Congolese Patriots (UPC) which now controls Bunia was originally backed by Uganda.
But then UPC leader Thomas Lubanga quarrelled with Uganda and his faction is now being armed by Rwanda.
Earlier this year, there were fears that Rwanda and Uganda might clash in Bunia because each was arming rival militias.
Last year's UN report into the looting of DR Congo said that senior Ugandan commanders had personally benefited from exploiting Ituri's natural resources.
It suggested that Mr Lubanga's UPC may be backed by "powerful Hema businessmen and politicians" trying to wrest control from the Ugandans.
Earlier this year, the Ugandans drove the UPC out of Bunia.
The Ugandans withdrew from Bunia last week following an agreement with the Congolese Government, leaving a power vacuum.
What is the United Nations doing?
Some 625 peacekeepers arrived in Bunia as the 6,000 Ugandans left two weeks ago but they have been unable to restrain thousands of ethnic militiamen.
Uganda's President Yoweri Museveni recently called them "useless".
"What they are doing right now is they drive around in their cars, remain in their cars while people are being killed 500 metres away. That is dangerous tourism. This is not acceptable," he said.
Some 600 Congolese police were also sent to Bunia to replace the Ugandans but 500 of them have run away.
Will the international community send more peacekeepers?
France has offered to send troops but this was immediately rejected by Mr Lubanga.
He says the French back Congolese President Joseph Kabila, who Mr Lubanga says is helping the Lendus.
Other big countries will be wary of getting bogged down in an extremely complicated and brutal conflict.
Mr Museveni has talked of an African force but in Ivory Coast, French peacekeepers have been more effective than the West African soldiers.
What has happened to the residents of Bunia?
Most of the 300,000 residents have fled the fighting but some 10,000 remain - mostly in and around the UN buildings.
Many thousands have crossed the border to Uganda, others have fled to the north of Bunia.
Babies and priests are among those who have been brutally killed.
Several mass graves have been discovered in the Ituri district.
Some 50,000 people have been killed in the region in recent years.