UN troops opened fire Wednesday on pro-government Congo militia who attacked them in the east of the strife-torn African country, the UN mission said.

Militia fighters fired on two UN armoured vehicles, said Lieutenant-Colonel Jean-Paul Dietrich, spokesman for the UN Mission in DR Congo (MONUC). The militia, however, accused the peackeepers of shooting first.

The clash erupted as Laurent Nkunda`s rebels withdrew from several districts in Nord-Kivu province where a new uprising against the government has grown in intensity in recent weeks. But the rebels are keeping up pressure on the regional capital Goma.

UN soldiers and so-called Mai-Mai militia men exchanged fire in a market in Kibututu, about 80 kilometers (50 miles) north of Goma.

Dietrich said UN troops `responded with light arms fire` after being shot at by the militia, stressing that this was to avoid civilian injuries in the market.

A Mai-Mai spokesman, Didier Bitaki accused the peackeepers of firing first.

He said a MONUC convoy `came to dislodge our forces from the main road... and to allow a CNDP convoy that was withdrawing to pass,` adding that the UN troops had `opened fire.`

`This type of error will no longer be tolerated,` he said, threatening to `become belligerent` with UN troops and attack Kiwanja, the scene of an earlier troubles involving the militia and which is now controlled by Nkunda rebels.

According to a rebel source at Kiwanja, the pro-government militia were on Wednesday around five kilometres (three miles) north of the town and many inhabitants had fled, fearing an attack.

Nkunda`s men were withdrawing from around two battlefronts some 80 kilometres (50 miles) northeast of Goma, MONUC confirmed.

But the rebels remained around 15 kilometres (10 miles) from Goma, the city of some 500,000 people and a large UN base.

Nkunda`s National Congress for the Defence of the People (CNDP), which said it was withdrawing from the zones in a bid to boost peace efforts by a UN envoy, accused the army of preparing to move into the evacuated zones.

It warned it would reverse the withdrawal if government forces moved into the vacated areas.