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.