The killings highlighted the inability of U.N. peacekeepers to protect civilians or halt a 10-week-old rebel offensive that has convulsed eastern Congo and forced more than 250,000 people from their homes.
The fighting in Congo is fueled by ethnic hatred left over from the 1994 slaughter of 500,000 Tutsis in Rwanda. Rebel leader Laurent Nkunda claims to be fighting to protect minority Tutsis from Rwandan Hutu rebels who participated in the genocide and then fled to Congo. He wants direct talks with President Joseph Kabila's government to end the fighting, and a rebel-declared cease-fire around Goma has mostly held.
Yet new fighting erupted Sunday around the town of Ngungu, 35 miles (60 kilometers) northwest of Goma, with rebels and soldiers firing mortars and rocket-propelled grenades, U.N. military spokesman Col. Jean-Paul Dietrich said. The rebels were also fighting pro-government Mai Mai militia there, he said
U.N. peacekeepers met with commanders of the three forces and persuaded them to stop after about six hours, Dietrich said.
Hundreds of refugees fled the fighting, gathering near a U.N. base for safety, he said.
Rebels and soldiers also clashed briefly at two villages north of Goma.
At least 50,000 refugees have crowded into Kibati, some taken into log cabins by villagers, others living in tents or hastily built beehive-shaped huts. Thousands who have no shelter and sleep out in the open huddled under pieces of plastic sheeting Sunday as curtains of rain pounded down.
Doctors Without Borders said it treated 13 new cases of cholera Sunday and has seen 45 cases at Kibati since Friday. The agency's Dr. Rafaela Gentilini said shortages of water and latrines were making the outbreak "really dangerous."
In a tented clinic, nurses put patients on IV drips. With treatment, patients can recover from cholera quickly. But Gentilini said they were transporting seriously ill patients to Goma Hospital each night because fighting has left them unable to treat people at night.
Dozens have died of cholera in recent weeks elsewhere in eastern Congo. Doctors also fear a cholera epidemic north of Goma behind rebel lines, where access has been limited by fighting and rebels have driven tens of thousands of people from camps where outbreaks had been contained.
Infected patients can spread the contagious disease, caused by unsanitary conditions, with just a handshake.
Tens of thousands of refugees already have fled from Kibati twice in the past 11 days, trying to avoid the fighting.
At Kibati's Roman Catholic Church, candles burned in supplication and people prayed that a fragile cease-fire between rebels and government forces would hold. Down the road, both sides faced off just 800 meters apart, but there was no fighting.
U.N. officials, meanwhile, say they are investigating alleged war crimes in recent fighting at Kiwanja, 50 miles (80 kilometers) north of Goma. They say residents first were terrorized by Mai Mai militia who killed people accused of supporting the rebels - then the rebels won control and killed those they claimed had supported the militia.
The rebels also looted and burned homes and a hotel, witnesses said.
Many victims were killed execution-style, with bullets to the head, residents told The Associated Press. Some residents said the rebels dressed the dead, most of them young men, in military uniforms.
U.N. investigators said at least 26 people were killed. But New York-based Human Rights Watch said it was trying to confirm reports of more than 50 dead, and blamed both sides for atrocities.
Associated Press reporter Michelle Faul contributed to this report from Goma, Congo, and AP photographer Karel Prinsloo reported from Kibati.