Goma - Rebels in the DRC on Tuesday seized the airport in Goma and were moving toward the centre of the main city in the mineral-rich east of the country, according to the UN and witnesses.
“The airport is under the control of the M23,” a United Nations official said on condition of anonymity, referring to the rebel group of former soldiers who mutinied in April, setting off the latest cycle of violence in the chronically unstable area.
A column of rebel fighters was seen heading from the airport toward Goma proper, several kilometres away, according to an AFP photographer on the scene.
Loud explosions shook the area and there were reports of looting.
The city of 300 000 is the regional capital and currently is also sheltering tens of thousands of refugees who have fled the clashes.
The international community has raised alarm about the fighting, which has sparked fears of a wider regional conflict in the region.
The UN accuses neighbouring Rwanda and Uganda of backing the rebels, charges both countries deny.
Washington has warned the fighting was “an extremely dangerous and worrying situation” and the EU, Britain and France have also raised alarm.
The latest round of fighting erupted last week - after the US and the UN slapped sanctions on the leader of the M23.
The rebels have said they plan to fight the DR Congo government “until it falls”, and the United Nations warned they have a real possibility of capturing Goma.
The UN has about 1 500 “quick reaction” peacekeepers in Goma, part of about 6 700 troops in the Nord Kivu province, backing government forces against the rebels.
Aid agencies have evacuated staff from the city and the UN had planned to remove non-essential personnel on Tuesday.
On Monday Kinshasa rejected the rebels ultimatum for direct talks within 24 hours, calling it “irrational rantings.”
“We prefer to negotiate with Rwanda, the real aggressor,” government spokesman Lambert Mende told AFP.
Rwanda late on Monday had accused government troops of deliberately bombing its territory.
The M23 rebels are former soldiers who mutinied in April after the failure of a 2009 peace deal that integrated them into the regular army.
The fighting is the most serious since July, when UN helicopters last went into action against the M23.
The mineral-rich east has long been a powderkeg, the launchpad of rebellions dating back to 1996, with Rwanda and Uganda both playing active or behind-the-scenes roles in much of the warfare.
Two wars that shook the whole of DR Congo between 1996 and 1997 and then again from 1998 to 2002 both began in the Kivu region.
Since 1998 more than three million people are estimated to have died from combat, disease and hunger and 1.6 million have been left homeless.
The former Belgian colony, known as Zaire under the dictator Mobutu Sese Seko who was toppled in 1997, remains one of the world's least developed countries despite a wealth of cobalt, copper, diamonds and gold.
In peaceful times, Goma is the starting point for tourists wishing to see endangered mountain gorillas in nearby Virunga National Park.