The UN Security Council is set to hold an emergency meeting on a new surge in fighting in eastern DR Congo amid reports of the killing of a peacekeeper and the discovery of two mass graves.
MONUSCO, the UN mission in eastern Congo, said a Tanzanian officer had been killed in Kiwanja, where peacekeepers joined the Congolese army to drive out M23 rebels on the third day of clashes since a fresh flare-up in violence on Friday.
The circumstances of the soldier's death were unclear, said MONUSCO, as a provincial governor alleged that mass graves had been discovered in the town.
Julien Paluku, the governor of North Kivu province, whose capital Goma has been a flashpoint in the conflict between Congolese troops and M23, called for "an international investigation".
Army troops had been told not to touch the bodies, Paluku said.
The UN issued a statement condemning the killing of the peacekeeper “who came under fire from the M23 in eastern Democratic Republic of the Congo", but stopped short of commenting on the mass graves.
"The Secretary-General offers his sincere condolences and sympathy to the family of the victim, and to the government of the United Republic of Tanzania," a spokesman for Ban Kimoon, the UN chief, said in a statement.
The statement added that the United Nations "remains committed to taking all necessary actions ... to protect civilians in eastern Democratic Republic of the Congo".
France later called for an emergency meeting of the 15-member Security Council to discuss the latest crisis in the troubled region.
M23, who take their name from a peace agreement they signed with the government on March 23, 2009 before reneging on it in April, said they had "retreated without combat", adding that they "refused to fight in Kiwanja".
In a statement, the group also threatened to pull out of stalled peace talks with the Congolese government unless there was an "immediate cessation of the hostilities".
In the town of Rutshuru, relieved residents "showered soldiers with flowers to thank them for their help" after the rebels fled, according to one local man who gave his name as Bruno.
There was no immediate comment from M23 rebels on the situation in the Kibumba, some 25km north of Goma.
Kibumba, located high on a plateau at an altitude of nearly 1,800 metres, is an outpost that provides access to rebel territory further north, and has been home to the M23 since a MONUSCO offensive in late August.
This latest bout of fighting comes less than a week after the breakdown of peace talks in Uganda, which both sides agreed to in 2012 after a rebel offensive saw the M23 briefly take control of Goma.
The UN has since deployed a special brigade of 3,000 African troops - from Tanzania, Malawi and South Africa - with an unprecedented offensive mandate but observers remain wary of an escalation that could draw in the entire region.
The UN chief's top envoys to the conflict, Kobler and Mary Robinson, have voiced grave concern over the fresh fighting, calling for "maximum restraint".
The United States and European Union have also sounded the alarm.
But the unrest showed no signs of abating with the M23 warning in a statement on Sunday that "it will no longer tolerate another military attack on our troops' positions".
If attacked, the rebels would plan a large-scale counter-offensive against "all enemy positions", M23 communications chief Amani Kabasha said in the statement.