Congo has severed diplomatic ties with Rwanda as fighting between Rwanda-backed rebels and government forces rages around the key eastern city of Goma.

The three-year insurgency by the rebel group M23 has intensified in January with the rebels seizing control of more of the central African country's territory than ever before, and the U.N. warning the violence could spill into a wider regional war.

Thirteen soldiers serving with peacekeeping forces in the Democratic Republic of Congo have been killed in clashes with rebels from the M23 group. The South African military said nine of its soldiers died helping to push back a rebel advance on the city of Goma,