Congolese Tutsi rebels and government troops have exchanged mortar and small arms fire in a clash in east Congo, a few kilometres from a refugee camp, Congolese and UN officers have said.

The fighting on Friday started as a shaky ceasefire collapsed and Joseph Kabila, the Congolese president, met his Rwandan counterpart Paul Kagame and Ban Ki-Moon, the UN secretary-general, to try to pacify the conflict-ravaged east.

The meeting is being held in the Kenyan capital Nairobi.

"We are hearing mortar and small arms fire," a UN military spokesman told the Reuters news agency.

He said the clash was reported near Kibati, about 7km north of Goma, the capital of Democratic Republic of Congo's North Kivu province.

Witnesses said hundreds of frightened civilians started fleeing from the camp towards Goma at the sound of the fighting, which forced the UN children's agency Unicef to halt a distribution of food supplies.

A column of Congolese troops was seen heading north into the bush, towards frontline positions occupied by rebels loyal to renegade General Laurent Nkunda, who suspended an offensive on Goma last week.

A Uruguayan UN commander on the spot said the troops reinforcing the government lines were Angolans, but this could not be immediately confirmed elsewhere.

Nkunda's rebels have accused the Congolese government of using Angolan troops.

General Vainqueur Mayala, who heads the Congolese troops in North Kivu, said there was a "clash" near Kibati between his troops and Nkunda's rebels.

There was no immediate report of casualties.