Tens of thousands of panicking Congolese are fleeing from their homes after heavily armed rebels made a dramatic advance to the outskirts of the strategic city of Goma, despite a wave of strafing attacks by United Nations helicopters.

Aid agencies estimate that 50,000 people are fleeing the sudden advance by the M23 rebels, who seemed poised on Sunday to capture Goma if they choose. Many foreign aid workers have withdrawn from the city, and thousands of people have abandoned a refugee camp in the path of the rebel advance.

Negotiations are underway, with the rebels seeking concessions from the UN and Congo in exchange for an agreement to stay out of the city. The rebels already seized control of a huge swathe of the mineral-rich province of North Kivu, which contains vast gold and other resources, and their advance to Goma will further consolidate their power in the region and control of its mineral wealth.

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Goma, the headquarters of UN peacekeeping forces in the eastern Democratic Republic of Congo, is a city of about a million people and the capital of an impoverished region that has been fought over in a series of wars and rebellions over the past 16 years.

On Sunday, UN leader Ban Ki-moon peacekeepers will stay in Goma and warned that any action that targeted them "will not be tolerated."

Rwanda, which recently became a member of the UN Security Council, is providing key logistical and financial support to the M23 rebels, according to several reports by UN investigators and others. Uganda is also believed to be supporting the rebels.

Rwanda and Uganda have denied the reports, but the UN has noted that the rebels have been mysteriously supplied with an arsenal of sophisticated weapons, including night-vision equipment and heavy 120-millimetre mortars. The rebels are unlikely to have acquired such weapons without major foreign support, and Rwanda and Uganda have played an active role in Congo for many years.

On Saturday, the rebels captured the town of Kibumba, about 30 kilometres north of Goma, as poorly paid Congolese soldiers fell back from the advance.

The UN Security Council held an emergency session on Saturday to discuss the Congo crisis, urging the M23 rebels to immediately halt their advance, and demanding a halt to foreign support for the rebels. The rebels ignored the plea and continued their offensive, reaching the outskirts of Goma on Sunday afternoon and setting up a front line about three kilometres outside the city, near the UN-controlled airport.

Four UN attack helicopters tried to stop the rebels, firing cannons and rockets at them on Sunday, but failed to halt the advance.

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Many people in Goma panicked when they saw Congolese soldiers rushing around the city as the rebels advanced. "The streets are deserted," said Luka Bakeni, a Congolese student in Goma who fled across the border to Rwanda on Sunday.

"Traffic and municipal transport have stopped moving," he said in an e-mail to a Canadian friend on Sunday. "Petrol stations, shops and businesses have closed their doors. The faithful few who tried to go to church had to turn back because of the growing panic in the city. The regular army has placed tanks in strategic places across the city, including along the road to the airport."

Connie Smith, a Canadian who works for a humanitarian organization in Goma, was instructed by her employer to leave Goma on the weekend for safety reasons. She crossed the border to neighbouring Rwanda, but could still hear the explosions from the fighting in Goma on Sunday.

Ms. Smith said the situation is a disaster for the people in the region. Her husband, who is still in Goma, told her that very few cars or motorcycles were moving in the city. Some of her relatives panicked and left Goma to join her in Rwanda.

The city is virtually besieged by rebels, with few escape routes, she said. "The M23 have circled around to a place called Sake, west of Goma, so there is no way to run there. To the north of us are the rebels. To the east is Rwanda, backing the rebels. To the south is Lake Kivu. So there are not a lot of options."

The M23 rebels, led by indicted war-crimes fugitive Bosco Ntaganda, took their name from a March 23, 2009, peace agreement that integrated the rebels into the Congolese army. They abandoned the agreement in April this year, defected from the army and began their march for control of eastern Congo.

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With a report from Reuters