* UN says rebels infiltrate east Congo city in "small numbers"
* Fighting inflaming tension between Congo and Rwanda
* Refugees flee Goma camps as fighting intensifies
* Uganda drops mediating role in protest at UN report (Adds further detail, background)
By Jonny Hogg
GOMA, Democratic Republic of Congo, Nov 20 (Reuters) - Rebels, widely believed to be backed by Rwanda, entered the city of Goma in eastern Democratic Republic of Congo on Tuesday, escalating clashes between the insurgents and U.N.-backed Congolese troops defending it.
The M23 rebellion has aggravated tensions between Congo and its neighbour Rwanda, which Kinshasa's government says is orchestrating the insurgency as a means of grabbing the chaotic region's mineral wealth. Rwanda denies the assertion.
A Reuters witness said fighters from the M23 rebel group were advancing by foot along the road to the city centre where sustained lights arms fire rang out - the first clear evidence they had entered the provincial capital of North Kivu province after days of fighting along the outskirts.
"What has probably happened is that they've infiltrated the town in small numbers," Lieutenant General Chander Prakash, the Goma-based force commander for the U.N. peacekeeping mission in Congo, known as MONUSCO.
He added that rebels had been pushed back by U.N. and army forces from Goma airport after a morning assault.
Streams of residents headed for the nearby border with Rwanda, saying they had been ordered to evacuate by the army. More than 50,000 people who fled fighting earlier this year have abandoned refugee camps around Goma, a city on the Rwandan border with a population of 1 million.
"With the war, we're suffering so much, I've never seen anything like this in my life," a woman who gave her name only as Aisha told Reuters, clutching her three children.
MUTINY
M23 is led by mutinying soldiers who rose up eight months ago, contending that Congo's government violated a 2009 peace deal that was meant to integrate them into the army.
U.N. experts, however, support the view that Rwanda, which has intervened in Congo repeatedly over the last 18 years, is behind the revolt.
Goma's capture would be an embarrassment for President Joseph Kabila, who won re-election late last year in polls that triggered widespread riots in Kinshasa and which international observers said were marred by fraud.
The vast central African nation was shattered by wars between 1994 and 2003 that killed about 5 million people. Many eastern areas are still plagued by violence from a variety of rebel groups, despite U.N.-backed efforts to defeat them.
The United Nations has about 6,700 peacekeeping troops in North Kivu, including some 1,400 troops in and around Goma.
Another neighbour of Congo, Uganda, blamed the escalation of fighting in eastern Congo on a leaked U.N. report that accused it and Rwanda of supporting Congolese rebels, a document Kampala said damaged its mediation efforts.
Uganda has vigorously denied the U.N. charges, which emerged in October, and Junior Foreign Affairs Minister Asuman Kiyingi said Kampala had been forced to retreat from its mediating role.
"Uganda was mediating in this conflict ... and we had managed to restrain M23," Kiyingi told Reuters.
"Then the U.N. comes up with these wild and baseless allegations against us and we decided to step aside and leave the situation to them and now you see the results," he said.
Uganda has threatened to pull its troops out of peacekeeping operations in Somalia unless the U.N. allegations are withdrawn. (Additional reporting by Elias Biryabarema in Kampala; Writing by Richard Valdmanis; Editing by Mark Heinrich)
Our Standards: The Thomson Reuters Trust Principles.
