But a Spokesperson for the Burundian military dismissed reports of the ongoing pull-out as "fake", and said in a post on X that his country's soldiers were "continuing to execute their missions in their areas of responsibility" in DRC.

The pull-out came as the United Nations (UN) human rights office accused M23 rebels of executing children in eastern DRC during their advance, which has seen the group seize the region's two largest cities.

"A number of trucks filled with (Burundian) military arrived in the country since yesterday" through a border post, a Burundian army officer said, confirming movements also described by two UN sources and an African diplomat.

Burundian soldiers fought alongside the Congolese to try to defend Kavumu, home to the airport that services Bukavu, the capital of South Kivu province, which fell over the weekend. It was the rebels' most significant prize since they seized Goma, the biggest city in eastern Congo, in late January.

Burundi has had soldiers in eastern DRC for years, initially to hunt down Burundian rebels there, but more recently, to aid in the fight against M23.

The well-equipped M23 is the latest in a long line of ethnic Tutsi-led rebel movements to emerge in Congo's volatile east.

In their march south, the rebels on Tuesday entered the town of Kamanyola, some 50 km (31 miles) south of Bukavu, according to two residents and an M23 source. A Congolese army Spokesperson did not immediately respond to requests for comment.

Fighting between rebels and the DRC army also took place on Tuesday in Lubero territory, north of Goma, local official Kambale Vighuliro and army colonel Alain Kiwewa told Reuters.

DRC President Felix Tshisekedi met his Angolan counterpart Joao Lourenco in Luanda, the Angolan capital, to discuss the accelerated deterioration of the security situation in eastern DRC, the Angolan presidency said in a statement posted on Facebook.

Rwanda rejects allegations from DRC, the UN and Western powers that it supports the group with arms and troops. It says it is defending itself against the threat from a Hutu militia, which it says is fighting with the DRCmilitary.

DRC rejects Rwanda's complaints and says Rwanda has used its proxy militias to loot its minerals.

On Tuesday evening Rwanda said it was suspending development cooperation with Belgium over what it called an aggressive campaign to sabotage Rwanda's access to development finance, including through multilateral institutions.

Various militias are vying for control of the region's abundant mineral resources such as tantalum and cobalt, key components of electric vehicles, mobile phones and other technological products used across the world.

DRC is also the top supplier of copper to China.

EXECUTIONS

In Geneva, the UN Rights Office said conditions were deteriorating sharply for civilians caught up in the fighting in eastern DRC, with reported abuses including summary executions and sexual violence.

"Our office has confirmed cases of summary execution of children by M23 after they entered the city of Bukavu last week," Spokesperson Ravina Shamdasani told a press briefing.

Three boys likely no older than 15 were killed during an altercation with rebels after they refused to give up weapons they had taken from an abandoned military camp, she said.

Between 10 000 and 15 000 people have crossed into Burundi from around Bukavu in recent days, straining resources and leading to overcrowding, Matthew Saltmarsh, Spokesperson for the UN refugee agency, said.

Some have drowned in the Ruzizi River while trying to cross, he said.

"(Refugees) are exhausted and traumatised. Many of them have been separated from their families with little information on their whereabouts," Saltmarsh said.

Boat traffic returned to Lake Kivu on Tuesday as ports re-opened in Goma and Bukavu, which the UN said could facilitate access to humanitarian aid after weeks of fighting and looting.

However, the airport in Goma, which the UN describes as a lifeline for aid, remains closed.

North of Goma, Uganda's army said it had entered the eastern DRC city of Bunia with approval from local military authorities to stop militia killings there.

--Reuters--