Renewed fighting is increasingly threatening the fragile peace deal agreed between the government and rebel groups and their foreign allies in Lusaka in August.

A spokesman for the rebel Congolese Rally for Democracy, Kin Kiey Mulumba, told the BBC that government troops had burnt down three villages in the area of Bokungu before being repelled by rebels.

The official said government aircraft later returned to bombard the area.

He added that fighting in the area was continuing.

The Goma-based rebels have already accused the government of seriously violating the ceasefire, as have the northern-based Movement for the Liberation of Congo (MLC).

The MLC also accused government forces of bombing its positions and was quoted as saying the ceasefire, which came into effect in August, was now "null and void".

There has been no word from the Congolese Government about the fighting and no independent confirmation.

UN moves

In a related move the United Nations has sent an envoy to Congo to secure commitments on all sides to the peace agreement.

President Kabila's government is accused of ignoring the ceasefire

The envoy, Mustapha Niasse, said after meetings with senior officials in the capital, Kinshasa, that the UN was determined to restore peace in Congo through a strict application of the Lusaka Accord.

A BBC correspondent in the region says the peace process has been marked by endless rows and recriminations and a hugely ambitious timetable has already fallen by the wayside.

Earlier, the presidents of Uganda and Rwanda - who are allies of the rebels - reaffirmed their commitment to the ceasefire at a meeting in Uganda.

On Monday, the US State Department condemned recent attacks by Congolese Government forces in Equateur province and a reported attack on civilians in rebel-based territory near the town of Uvira in South Kivu province.

"These attacks are a clear violation of the Lusaka Accord signed by the states and the rebel groups involved in the conflict," State Department spokesman James Rubin said.