By Greg Barrow BBC United Nations correspondent, New York

Rwanda and the Democratic Republic of Congo have swapped accusations over recent fighting in DR Congo, bringing last month's peace deal into question.

When you decide to make peace, you make peace

Anastase Gasana Rwanda

After a fresh round of fighting between Rwandan troops and armed groups in the South Kivu area of eastern DR Congo, the Congolese ambassador to the United Nations accused Rwanda of a flagrant violation of the ceasefire.

Rwanda has now hit back.

It says its troops were forced to act because Kinshasa is continuing to offer moral, political, and material support to elements of the former Rwandan army, and Rwandan Hutu militia groups, based in south Kivu.

Under the terms of the Pretoria peace accord, the Congolese government was meant to stop assisting these groups.

Peacekeepers

The Rwandan ambassador to the UN, Anastase Gasana, said that as far as Kigali was concerned, entering into a peace agreement was an all-or-nothing affair.

Rwanda agreed to withdraw if ethnic Hutu militias were disarmed

"When you decide to make peace, you make peace. You can't make peace, half peace or a quarter peace or three-quarter peace," he said.

This latest exchange between the Rwandan and Congolese diplomats only emphasises the importance of boosting the presence of outside observers in areas like eastern DR Congo, where foreign troops are in close contact with opposing forces.

UN officials are currently working on a plan that could see the deployment of South African soldiers in places where there could be a security vacuum once foreign troops withdraw.