The UN Security Council is to hold a special session on Monday to discuss the latest surge in violence between M23 rebels and government troops in the eastern Democratic Republic of the Congo.
The clashes last week followed a breakdown in peace talks between the two sides.
The army says it has taken control of Rutshuru, a key rebel stronghold located about 70 kilometres north of Goma, the main city in the east.
Last year, M23 briefly took control of Goma before retreating and agreeing to talks with the government.
The group that was formed in early 2012 by former rebels who had been integrated into the army but defected has been split by infighting as it faces heavy assaults by the government.
A new UN intervention force, about 3 000 strong, has since been deployed to the volatile region to provide support to the weak and disorganized Congolese army.
UN Secretary General Ban Ki-moon has condemned the killing of a Tanzanian peacekeeper over the weekend.
The UN says its military operation in the country, consisting over over 20 000 troops, is on “high alert.”
A UN panel of experts found Congo’s neighbours Rwanda, and to a lesser extent Uganda, to be aiding the rebels. The two countries deny this.
Mary Robinson, the UN special envoy to the Congo, said the last round of peace talks broke down over the issues of amnesty, disarmament and integration of M23 fighters.