Nairobi - The top United Nations envoy to the Democratic Republic of Congo has appealed for more soldiers as rebel forces threaten to overwhelm government and UN peacekeepers in the eastern part of the Central African nation.

UN helicopter gunships and armoured vehicles have been supporting Congolese troops north of Goma, the capital of North Kivu province, as renegade Tutsi general Laurent Nkunda's troops press toward the town.

Nkunda's National Congress for the Defence of the People (CNDP) has reportedly driven the Congolese army back from the town of Kibumba, which lies about 20 kilometres north of Goma.

The UN has only 6,000 troops in the area - out of a total of 17,000 in the sprawling country - and they are being stretched to the limit.

Alan Doss, the head of the UN mission in DR Congo, told the BBC Tuesday he needed urgent reinforcements, but that his soldiers would try to prevent major towns falling to the CNDP.

Fighting has also broken out near the town of Rutshuru, 100 kilometres north of Goma, prompting plans to evacuate foreign aid workers based there. However, locals angry at the UN for failing to protect them are reported to have blocked attempts to get the workers out.

Angry demonstrators stoned UN compounds in Goma on Monday and Tuesday, saying that peacekeepers had failed to do enough to protect civilians.

The UN mission said peacekeepers were forced to intervene, and that one civilian was killed in the rioting.

Tens of thousands of civilians have fled the advance of the rebels toward Goma, which Nkunda has threatened to take.

The CNDP and other groups in January signed peace accords designed to end sporadic clashes that occurred in 2007, four years after the war officially ended.

But the CNDP and government soldiers have been involved in repeated clashes in the eastern North and South Kivu provinces since late August.

Aid agencies say well over 100,000 civilians have fled the renewed fighting since August, joining hundreds of thousands of displaced in the region, and are warning of an impending humanitarian disaster.

"The population here had already reached its coping capacity before recent events," said Luke King, Mercy Corps' Country Director in the DR Congo. "Without resources for continued services, we expect a steep increase in malnutrition and diarrhoea-related diseases."

More than 5 million people are estimated to have died as a result of the long war in the resource-rich nation, most of them due to hunger and disease.

The conflict is often referred to as the African World War owing to the large number of different armed forces involved.

Observers are concerned that the new clashes could re-ignite a wider conflict and plunge the country back into chaos.

Nkunda's troops say they are fighting to protect Tutsis from armed Hutu groups.

Many of the Hutus fled to DR Congo after the 1994 massacre in Rwanda, when Hutu militia and military killed an estimate 800,000 Tutsis and moderate Hutus in the space of a few months.

The DR Congo government recently accused Rwanda of amassing troops on the border with a view to backing Nkunda and attacking Goma. (dpa)