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By Hez Holland

GOMA, Congo, Oct 28 (Reuters) - U.N. peacekeepers prepared on Tuesday to evacuate around 50 foreign aid workers from a town in eastern Congo, which Tutsi rebels are advancing on, officials said.

The rebels fought their way along a road towards Rutshuru, about 100 km (60 miles) north of North Kivu's provincial capital Goma on Tuesday, drawing within 10 km (6 miles) of the town.

"The convoy is being prepared now, but hasn't left yet," a spokesman for U.N. humanitarian coordination agency OCHA said. "It will leave today. Normally there are around 50 staff in Rutshuru and surrounding areas."

The U.N.'s peacekeeping mission, MONUC, sent attack helicopters against rebel positions north of Goma on Monday, prompting anti-aircraft fire from Nkunda loyalists.

"MONUC will use all available means to protect urban centres including Rutshuru, Sake (to the west of Goma), and Goma," said Michel Bonnardeaux, spokesman for the U.N.'s biggest peace force, with 17,000 personnel based mainly in the east of Congo.

Rutshuru shelters tens of thousands of internal refugees displaced by nearly two years of on-off fighting in North Kivu.

Tuesday's advance comes a day after insurgents attacked the town of Kibumba, 20 km (12 miles) north of Goma, sending around 20,000 refugees fleeing towards the provincial capital.

An aid worker with medical charity Medecins Sans Frontieres (MSF) told Reuters its staff in Rutshuru could hear explosions from its headquarters at the main hospital early on Tuesday.

"In Rutshuru, the population is fleeing north. We've heard about an evacuation, but for the moment we have no plans to leave," said Axelle de la Motte Saint-Pierre, MSF's deputy head of mission in North Kivu.

She said MSF's medical team there had treated around 70 people wounded in fighting since the offensive began on Sunday.

"TOTAL PANIC"

"There is total panic in town. The fighting is now around 5 km (3 miles) from Rutshuru," local administrator Dominique Bofondo said by telephone.

U.N. sources said fighting at Kibumba had eased following early morning clashes on Tuesday, and peacekeepers were reinforcing positions there.

However, a Reuters witness saw a column of soldiers returning towards Goma in disarray in an apparent retreat.

"A huge amount of army are pulling back. It's a massive amount of people," he said.

Congo's European Commission mission said Louis Michel, EU commissioner for development and humanitarian aid, would make an emergency visit this week to the capital, Kinshasa.

U.S. Assistant Secretary of State for African Affairs Jendayi Frazer was due to arrive in Congo on Thursday.

Nkunda's National Congress for the Defence of the People (CNDP) accuses Congo's army of collaborating with the Democratic Forces for the Liberation of Rwanda (FDLR), which includes Hutu militias and ex-Rwandan soldiers responsible for orchestrating Rwanda's 1994 genocide of Tutsis and moderate Hutus.

Around 250,000 civilians have fled homes in North Kivu since a January peace deal collapsed in August. According to the U.N., nearly two years of sporadic fighting had already displaced around 850,000 people before the latest round of fighting began.

Congo's 1998-2003 war and resulting humanitarian crisis have killed an estimated 5.4 million.

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