The Congolese army has called on the Rwanda-backed rebels fighting in the eastern Democratic Republic of Congo to surrender and save their lives.

On Wednesday, the Armed Forces of the Democratic Republic of Congo (FARDC) recaptured Bunagana, one of the last remaining strongholds of the March 23 movement (M23), raising hopes that the end to the 18-month-old rebellion is near.

The rebels fled to the nearby hills where about 200 die-hard fighters are still holding up at an altitude of about 2,000 meters.

The army is preparing to launch a final offensive against the M23 rebels, who defected from the FARDC in April 2012 in protest over alleged mistreatment in the army.

On Friday, Congolese army spokesman Olivier Amuli said the rebels were "caught in a vice".

"We are giving a final chance to all M23 fighters to surrender," Amuli said, as the army carried out mopping up operations to end the insurgency.

The UN peacekeeping mission in Congo, known as MONUSCO, said that "several dozen" M23 rebels had surrendered to the UN peacekeepers.

On Monday, UN special representative to Congo Martin Kobler told the Security Council, "We are witnessing the military end of the M23."

"Practically all M23 positions were abandoned yesterday, except for a small triangle at the Rwandan border," said Kobler, who is also the head of the 20,000-strong MONUSCO.

He said the M23 had abandoned a key position on Mount Hehu near the Rwandan border, adding, "It is practically the military end of the M23."

Speaking to the nation on Wednesday night, Congolese President Joseph Kabila asked the remaining M23 rebels to surrender, saying, "I reiterate my call to the members of this armed group who have just been flushed out of our territory... to demobilize themselves voluntarily."

"Failure to do so will leave us with no option but to force them to do by force," he stated.

The M23 rebels and several other armed groups are active in the eastern Congo and are fighting for control of the country’s vast mineral resources, such as gold, the main tin ore cassiterite, and coltan (columbite-tantalite), which is used to make many electronic devices, including cell phones.

Since early May 2012, nearly three million people have fled their homes in the eastern Congo. About 2.5 million have resettled in Congo, but about 500,000 have crossed into neighboring Rwanda and Uganda.

Congo has faced numerous problems over the past few decades, such as grinding poverty, crumbling infrastructure, and a war in the east of the country that has dragged on since 1998 and left over 5.5 million people dead.