The M23 have lost their last stronghold after Democratic Republic of Congo troops captured the area, which is the rebels' main base.
Congolese troops on Wednesday captured Bunagana, the main M23 rebel base near the eastern border with Uganda, driving the M23 rebels from their last stronghold, a government spokesperson said.
"Bunagana is completely under our control. We had been fighting since the early morning," said Lambert Mende, adding that the rebels had either fled into the mountains or crossed into neighbouring Uganda.
"Bunagana is in our hands", one soldier said. An officer from the UN mission in the country also confirmed that troops had taken control of the town, which lies about 80km north of Goma, the capital of the turbulent North Kivu province.
Troops and tanks had surrounded the nearby town of Rutshuru on Tuesday, the army said, in preparation for Wednesday's assault in the lush green hills near the eastern border with Uganda.
The fall of Bunagana comes a day after the head of the UN peacekeeping mission in Democratic Republic of Congo, Monusco, Martin Kobler, declared that the push by troops signalled "practically the military end of M23".
Kobler told the UN Security Council late on Monday that "practically all M23 positions were abandoned, except for a small triangle at the Rwandan border".
Congolese troops backed by a UN intervention brigade launched a major offensive at the weekend against the M23 rebel movement of army mutineers in North Kivu.
At least 5 000 people have fled into Uganda to escape the fighting, which has moved close to the border.
That figure could double, warned Lucy Beck, a spokesperson for the UN refugee agency UNHCR.
"We are predicting up to 10 000 people would have crossed by tomorrow, because the fighting seems to be going on very close to the border ... People are continuing to cross even as we speak," she said Wednesday.
Other aid groups estimated that around 22 500 people had left their homes to move closer to Goma, which is controlled by government forces.
In the Ugandan capital Kampala representatives from both sides were hoping to resurrect stop-start peace talks that stalled once again last week.
The joint head of the M23 delegation, Roger Lumbala, said delegates were "putting the final touches to a deal proposed by Ugandan mediators. I think ... tomorrow [Friday] or the next day we'll have signatures on this agreement".
A more measured Francois Muamba, representing Kinshasa, said: "If what we have put on the table is accepted by the M23, with or without pressure, I think things will move forward."
Bertrand Bisimwa, M23's political leader who has fled to Uganda, is due to take part in the Kampala talks.
After a two-month lull, clashes between rebels and the army flared again on Friday in North Kivu, a province rich in minerals and agricultural produce that armed groups have fought over for more than two decades.
Over the weekend, amid fierce fighting, government troops took control of a military base at Rumangabo and recaptured another town, Kiwanja, and Rutshuru, from where they were able to take Bunagana.
Alarmed by the renewed violence, the West called for restraint, with the US warning that the conflict could submerge the whole region.
The M23 was founded by former Tutsi rebels who were incorporated into the Congolese army under a 2009 peace deal they said was never fully implemented.
They mutinied in April 2012, turning their guns on their former comrades and launching the latest rebellion to ravage DRC's mineral-rich and conflict-prone East.
Despite its limited numbers – experts estimate the movement's fighters to now number less than 1 000 – the M23 has been seen as a threat to stability in an already volatile region with a long history of conflict.
The UN and numerous rights groups have accused the M23 of atrocities including rape and murder.
Both Kinshasa and the UN allege support for the rebels from Uganda and Rwanda, a claim both countries reject. – AFP