Gunfire and explosions shook Bujumbura after the Government deployed helicopter gunships to repel a surprise advance by about 2,000 members of the National Forces of Liberation (FNL), Burundi’s second-largest rebel group, which had taken them deep into the capital’s affluent eastern suburbs. More than 200 people have been killed and thousands forced to flee their homes after a week of fighting in which Hutu rebel leaders have vowed to bring the war to the heart of the city, threatening the fragile transitional Government.

Images of the dead and mutilated bodies of the youthful combatants have been broadcast on local television, provoking an outcry from aid workers and rebel leaders. Yesterday the US State Department ordered the evacuation of all non-essential staff from the US Embassy.

The FNL, which has been fighting since 1993 to end the political domination of the minority Tutsis, is opposed to the ethnically mixed Government. It has demanded the resignation of President Ndayizeye, a Hutu, who took over from Pierre Buyoya, a Tutsi, in April. They regard Mr Ndayizeye as a Hutu sellout.

Agathon Rwasa, the FNL’s leader, says that Hutus, who make up 85 per cent of the population, have a divine right to rule. He refuses to recognise the Government set up 20 months ago after Nelson Mandela intervened in an effort to end the ethnic conflict. The rebel advance has greatly alarmed South Africa, which has deployed peacekeepers to support the Government.

Dismissing allegations that Hutu fighters had been rounding up and killing civilians, Pasteur Habimana, the FNL spokesman, said: “The hostages were Tutsis captured by Hutus. They were kept under good conditions. We want the army to treat our hostages humanely and stop showing images of dead combatants on television.”

Burundi was plunged into civil war in 1993 when the Tutsis, who had ruled since independence from Belgium in 1962, assassinated Melchior Ndadaye, the Hutu President. More than 300,000 people have died in the fighting.