Congo asked Angola for political and military support on Oct. 29 as rebels led by Tutsi former general Laurent Nkunda advanced toward Goma, capital of North Kivu province near the border with Rwanda. Nkunda called a unilateral cease-fire last week when his forces reached the outskirts of the city, but the truce has crumbled amid persistent reports of fighting in the last few days.
A U.N. official and a Uruguayan peacekeeping officer said Friday that an unspecified number of the Angolans troops arrived four days earlier. The two officials spoke on condition of anonymity because of the subject's sensitivity.
The involvement of the Angolans could escalate and spread the conflict beyond Congo's borders. Neighboring Rwanda likely will consider the Angolan troops a provocation. Rwanda's Tutsi-led government is accused of supporting the Congolese rebels.
U.N. Secretary-General Ban Ki-moon, holding a peace summit in Nairobi, Kenya, with Congolese President Joseph Kabila and six other African leaders, said the U.N. peacekeeping force was stretched to the limit as the Congo fighting threatens to spread.
"We must put the cycle of violence behind us," Ban said. "This crisis could engulf the broader sub-region."
Violence has continued for years in eastern Congo, and wars there from 1996-2002 drew in more than half a dozen African nations. Since fighting intensified in August, around 250,000 people have been displaced.
The conflict is fueled by ethnic hatred left over from the 1994 slaughter of a half-million Tutsis in Rwanda. Nkunda claims he is fighting to protect minority Tutsis from Rwandan Hutu rebels who participated in the genocide and fled to Congo afterward.
A top African official at the summit criticized the U.N.
peacekeeping force - known by the French acronym MONUC.
"MONUC has failed," said Eddie Kwizera, Ugandan President Yoweri Museveni's top aide on relations with Congo.
Thousands of refugees gathered Friday outside the fenced compound of U.N. peacekeepers north of Goma, near Kiwanja, and complained to an Associated Press photographer that the peacekeepers gave them no protection when their town was attacked.
The refugees, who are sleeping in the open amid daily tropical rainstorms, said they have not eaten since the fighting began Tuesday and have received no food, water or any other help from the peacekeepers.
U.N. military spokesman Maj. Shardool Sharma said earlier Friday that the army fired mortars at rebels just north of Kibati and rebels responded with gunfire.
Some bursts of distant machine-gunfire were audible in Goma.
There were no immediate reports of casualties at the village of Kibati, six miles (10 kilometers) north of Goma. But the road south toward Goma was again lined with refugees fleeing the conflict, as it had been last week.
The U.N. refugee agency said the shooting lasted around 30 minutes, interrupted aid distributions and caused panic among the camp population.
The U.N. said rebels on Thursday captured a North Kivu army base at Nyanzale. Rebels also battled a pro-government militia known as the Mai Mai in Kiwanja on Tuesday and Wednesday, leaving at least 20 people dead, according to New York-based Human Rights Watch.
Both towns are north of Goma.