M23 rebels stand at a small base in the hills of Kanyarucinya on the outskirts of Goma, in the east of the Democratic Republic of the Congo, on Nov. 19, 2012. (PHIL MOORE/AFP/GETTY IMAGES)

Rebel forces in Congo on Tuesday seized control of Goma, a strategic provincial capital in the nation’s resource-rich east, despite the presence of U.N. peacekeepers in the area. The takeover sent tens of thousands fleeing and triggered fears of a regional conflict, according to officials and witnesses.

“The atmosphere in the city is tense, people are worried,” Grace Tang, head of mission in Goma for the aid group Doctors Without Borders, said in a statement before the takeover. “The fighting that for months has forced hundreds of thousands to flee their homes elsewhere in the region has now reached Goma’s doorstep.”

By Tuesday afternoon, the M23 rebels, formed earlier this year, had taken control of many of Goma’s streets and the international airport, according to news reports.

In New York, France and the United States agreed on a draft U.N. resolution — which was expected to be voted on Tuesday night — that condemns the rebels’ capture of Goma and demands their immediate withdrawal from the city.

This nook of Africa has been in a state of perpetual instability for many years. Congo has been besieged by conflict ever since the fall of longtime dictator Mobutu Sese Seko in 1997. Various rebel groups and the armies of several nations have fought over the eastern part of the country and its resources, which include vast deposits of tin, gold and tantalite, a mineral used in cellphones and laptops. The fighting has left millions dead, mostly from disease and starvation.

The International Crisis Group, a respected think tank, said in a statement Tuesday, “The past week has shown history repeating itself in eastern Democratic Republic of Congo, with the same tragic consequences for civilians in the region.”

State Department spokeswoman Victoria Nuland called the situation “very dangerous, very worrying.”

“We condemn the ongoing violent assault of M23 and the fact that it’s now taken Goma in violation of the sovereignty of the DRC,” she said.

The M23 is mostly made up of fighters from a previous rebel movement that threatened to seize control of Goma, a city of 1 million people, in 2008. The rebels and the government signed a peace deal on March 23, 2009, that called for the rebels to be integrated into the national army. The M23 is named for that agreement.

But the pact fell apart this April, and as many as 700 soldiers, mostly former rebels, defected from the military and launched the M23 movement. This time they didn’t stop on the outskirts of Goma, as they did in 2008.

The renegades are led by Bosco Ntaganda, wanted on war crimes charges by the International Criminal Court at the Hague. The United Nations has accused him and other senior commanders of summary executions, rape and the use of child soldiers.

U.N. officials have also accused neighboring Rwanda of backing the rebels, which Rwandan President Paul Kagame has denied. A 44-page U.N. report by experts monitoring an arms embargo in Congo found that Rwandan officials have played a leading role in the rebellion, including financing the insurgents and providing them with sophisticated military equipment.

For years, the United Nations has had thousands of peacekeepers in Congo, the largest such force in the world, yet they have failed to prevent successive rebel movements from gaining territory. This time around, the U.N. force, known by the acronym MONUSCO, did not have a mandate to fight the M23 rebels.

On Tuesday, French Foreign Minister Laurent Fabius declared that it was “absurd” that a few hundred rebels were able to seize Goma and urged a review of the U.N. mandate. “MONUSCO is 17,000 soldiers, but sadly it was not in a position to prevent what happened. It is necessary that the MONUSCO mandate is reviewed,” Fabius told reporters.

Colum Lynch at the United Nations contributed to this report.