The Congolese army said it has made significant advances against rebel forces in a third day of fierce fighting and called on neighbouring Rwanda to help disarm the fighters.
The military said on Sunday that it had taken back two more towns in eastern Democratic Republic of Congo after on Saturday forcing the rebels out of Kibumba, a town 20km north of Goma, the largest city in the region.
We have pushed M23 into the hills on the Rwandan border. We now call on Rwanda to help us disarm the fighters.
Army spokesman Lt. Col. Olivier Hamuli told The Associated Press news agency that the army took Kiwanja and Buhumba towns in the Rutshuru area of North Kivu province, near Congo's border with Rwanda.
Congolese forces and M23 rebels have been fighting heavily since Friday, the first clashes in two months, after peace talks in Uganda broke down this week.
"We have pushed M23 into the hills on the Rwandan border," Hamuli told Reuters news agency. "We now call on Rwanda to help us disarm their fighters."
The army "has launched an offensive on the Mabenga-Kahunga road. It is using troops, tanks and mortar shells", another army officer said.
M23 said in a statement on Saturday that the army had launched a "generalised attack" on several fronts, but that the fighting was turning in its favour
"It's heating up on all fronts," the M23's political leader Bertrand Bisimwa said on the group's website, confirming that the fighting had spread north.
Calls for calm
Rebels said the army attacked their positions early on Friday, but the military insisted it came under attack first - a claim supported by a source from the UN peacekeeping mission in the country, MONUSCO.
On Friday, Rwanda's UN ambassador told a closed-door meeting of the UN Security Council that shells fired by the Congolese army had landed in its territory and that it could respond militarily, diplomats said.
UN investigators have accused Rwanda of supporting M23, a charge it has denied.
The rebels take their name from a peace agreement they signed with the government on March 22 2009, paving the way for their integration into the national army, but they mutinied in April 2012 over poor salaries and living conditions, renewing an armed rebellion in the country's mineral-rich east.
In a joint statement, UN special envoy to the Great Lakes region, Mary Robinson, and head of MONUSCO Martin Kobler urged restraint and called on both sides to return to the negotiating table in Uganda's capital Kampala, where on-and-off peace talks between the government and M23 have been held since December.
The United States also said it was alarmed at the reports of increased fighting, despite international calls for restraint.