UN helicopter gunships opened fire on fighters loyal to a renegade Congolese warlord yesterday in an attempt to prevent the fall of a key town in eastern Democratic Republic of Congo to one of the country's most feared rebel groups.

The UN mission in the country said that its peacekeepers strafed rebel Tutsi forces loyal to General Laurent Nkunda in the Kibumba area as they advanced along the main road towards the strategic town of Goma, the capital of North Kivu province.

Bertrand Bisimwa, a spokesman for fighters of General Nkunda's National Congress for the Defence of the People, said they had encircled Goma, but that could not be verified independently.

The insurgents attacked Kibumba, home to thousands of displaced people, on Monday. Many terrified refugees have fled along the road towards Goma on Lake Kivu, 12 miles farther south. General Nkunda's Tutsi forces have a fearful reputation for rape, murder and looting, gained in the country's 1998-2003 civil war, by far the world's bloodiest recent conflict, in which more than five million people were killed.

Yesterday the Tutsi rebels said that they had overrun the eastern town of Rutshuru in an offensive against government troops in North Kivu province. “We have taken the town of Rutshuru and the [adjoining] town of Kiwanja,” Mr Bisimwa told Reuters by telephone.

Earlier Colonel Delphin Kahimbi, the head of the government Army's operations in the area, said he would have to abandon the town in the face of the rebel advance. Its fall would be a huge setback to the new national Army, a motley collection of former rebel forces that lacks the firepower to resist the Rwandan-backed rebels.

UN peacekeepers called off plans to remove about 50 foreign aid workers from Rutshuru because of mounting insecurity in the area. “They were blocked by the population and soldiers,” Colonel Kahimbi said.

General Nkunda has resisted incorporation of his forces into the national Army after a peace deal that ended the civil war.Goma is on the border with Rwanda, where the Tutsi-led Government backs General Nkunda. He claims to be protecting Congolese Tutsis against Hutu groups that fled Rwanda after carrying out the 1994 genocide of its much larger Tutsi population. Rwanda accuses Congo's new Government of failing to bring Hutu rebels to justice.

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