Rebels fleeing advancing government soldiers in the Democratic Republic of Congo have been accused of committing atrocities as they retreated.
Government troops told Al Jazeera on Saturday that they had discovered freshly dug graves in the last stronghold of the M23 rebels, close to the Ugandan border.
Al Jazeera's Malcolm Webb was shown one such grave at the Rumangabo base and said it looked like a man buried there had been executed.
"It looks like he was tied up, with his arms behind his back, and his legs tied together, at the moment he died," he said. "There’s some blood coming from his head, so it really looks like he was executed."
Some fighters who surrendered after government forces moved in said the rebel group killed its prisoners before it left.
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People living in the villages around the base told Al Jazeera that living conditions under the rebels had been harsh.
"They would beat people for nothing, and they would arrest people and make them disappear," one woman said.
On Friday, the government urged rebel fighters who had fled into the hills to surrender and avoid a final offensive to wipe them out.
About 200 die-hard fighters were holed up in the mountains, at an altitude of about 2,000 metres, near the eastern town of Bunagana, said government spokesman Lambert Mende.
After more than a week of heavy fighting around the town in the lush green, hilly region bordering Uganda, army spokesman Olivier Amuli told AFP 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 operations in a bid to put an end to an armed uprising in the restive North Kivu province.
UN patrols on Friday streamed through on the road leading to Bunagana, a small town without electricity or running water, secured by about 100 army troops.
About 5,000 people have taken refuge across the border in Uganda since the beginning of the week according to the UN's refugee agency.
Bunagana mayor Leon Bitegeka said "streams of people continue to cross into Uganda" due to the heavy fighting which began eight days ago.
The M23 are mainly ethnic Tutsis and were once part of the country's army, but mutinied last year, accusing the government of not honouring a 2009 peace deal.
The fighting stopped earlier this year, but restarted last month after peace talks broke down.
The world's largest UN peacekeeping force is in Congo, helping the government fight M23. Rwanda and Uganda have been accused by Congo's government and the UN of backing the rebel forces, but have repeatedly denied the allegations.
While no death tolls from the latest fighting have been released, the International Committee of the Red Cross said it was treating many wounded and had volunteers collecting and burying the dead.