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Congolese Tutsi rebels were pulling back south "in the hundreds" from frontline positions in North Kivu province in a gesture to support a United Nations peace initiative, a U.N. military spokesman said on Wednesday.

The withdrawal by rebel General Laurent Nkunda's National Congress for the Defence of the People (CNDP) fighters followed a commitment made by Nkunda at the weekend to a U.N. envoy that he would take part in peace talks and respect a ceasefire.

"Since yesterday evening they (the rebels) have been withdrawing. They are pulling back south on three axes - from Kanyabayonga towards Kibirizi, from Kanyabayonga towards Nyanzale and from Rwindi south," U.N. military spokesman Lt-Col Jean-Paul Dietrich told Reuters.

He said U.N. peacekeepers were monitoring the pullback and that the withdrawing rebels were estimated "in the hundreds".

Nkunda's rebels were pulling back south from territory they had occupied in recent weeks, routing demoralised government troops, more than 100 km (60 miles) north of Goma, capital of Democratic Republic of Congo's North Kivu province.

But they also hold strategic positions just 15 km (nine miles) north of Goma, near Kibati, and the CNDP statement announcing the planned pullback on Tuesday had made no mention of any withdrawal from the specific Goma front.

U.N. special envoy Olusegun Obasanjo, a former Nigerian President, is trying to set up peace talks in Nairobi between Nkunda, Congolese President Joseph Kabila's government and Great Lakes neighbour Rwanda to end the North Kivu conflict which has driven hundreds of thousands of civilians from their homes.