Nairobi /Goma - A fragile ceasefire in the east of the Democratic Republic of Congo has broken down as rebels who last week launched a major offensive once more battled the Congolese army, the United Nations peacekeeping mission in the African nation said Thursday.

Rebel Tutsi general Laurent Nkunda's National Congress for the Defence of the People (CNDP) called a ceasefire last Wednesday after its four-day offensive took it to the edge of Goma, the capital of North Kivu province.

However, after two days of small-scale clashes with the Mai-Mai pro-government militia, the CNDP on Thursday attacked the Congolese army.

"We have received confirmation that the CNDP has attacked the area of Nyanzale," Lieutenant Colonel Jean-Paul Dietrich, spokesman for the DR Congo peacekeeping mission (MONUC) told Deutsche-Presse-Agentur dpa. "The CNDP has broken its own ceasefire."

Dietrich said that government troops were forced to abandon their HQ at Nyanzale, North Kivu, amid heavy fighting. The nearby locality of Kikuku was also captured.

The civilian population around Nyanzale fled the fighting and took refuge near the MONUC base on the outskirts of the town, Dietrich said.

Aid agencies say that renewed fighting between the CNDP and government forces has displaced at least 250,000 people since late August.

As many as 50,000 of these people fled during four days of fighting last week, many of them to the area around Goma, the capital of the North Kivu province.

The breakdown in the ceasefire came as regional leaders prepared to travel to Kenyan capital Nairobi for a Friday summit aimed at ending the conflict.

The presidents of DR Congo and Rwanda, Joseph Kabila and Paul Kagame, are to attend the summit, as is UN Secretary General Ban Ki-moon.

Western diplomats feel that bringing Rwanda and the DR Congo together at the table is key to resolving the conflict.

DR Congo has accused Rwanda of backing Nkunda, who says he is fighting to protect Tutsis from armed Hutu groups who fled to DR Congo after the 1994 massacres in Rwanda, when 800,000 Tutsis and moderate Hutus were killed.

However, many analysts say that the ethnic dimension of the conflict is just a smokescreen for militias to grab a slice of DR Congo's rich mineral deposits.

Nkunda, who accused the Congolese army of starting the latest round of fighting, has said that he is ready to take Goma and also continue onto the capital, Kinshasa, on the other side of the massive country.

The UN peacekeeping mission has vowed to defend Goma.

The Under-Secretary-General of Peacekeeping Alain LeRoy said Wednesday that MONUC was reinforcing its positions in North Kivu, particularly in Goma.

However, while MONUC backed up the Congolese army during the CNDP offensive, it was unable to hold back the rebel tide.

MONUC chief Alan Doss said last week that his troops, numbering 17,000 across the whole of the sprawling central African nation, were stretched to their limit by the conflict.

Calls for more UN troops to be deployed in the country have so far not been answered with any firm commitments, although a UN Security Council meeting to approve the deployment of another 3,000 troops is mooted for late November.

Aid agencies and lobby groups are concerned that a fully fledged humanitarian catastrophe is in the making.

"The situation in the DRC remains on the brink of a humanitarian catastrophe," Amnesty International said in a statement Thursday. "The priority at the moment is reinforcing the capacity of ... MONUC, to protect civilians and to ensure people have access to humanitarian assistance."

The UN refugee agency, UNHCR, which on Wednesday along with the World Food Programme (WFP) began distributing food in North Kivu, warned that the fresh fighting could jeopardize the delivery of aid.

The WFP on Wednesday began handing out 10 days of rations, including high energy biscuits, to 135,000 people living in camps around Goma.

However, aid is not reaching many people trapped behind rebel lines, while others are reportedly living in the forests and subsisting on roots and berries.

Conflict has been rumbling on in the DR Congo since the official end of the war in 2003. The CNDP and other groups signed up to peace accords in January designed to finally bring the fighting to an end, but the civilian population has continued to suffer.

More than 5 million people are estimated to have died as a result of the 1998-2003 war in the resource-rich nation, most of them from hunger and disease.

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