One government source, the Justice Minister, Mwenze Kongolo, was quoted by the French news agency as saying the rebels had fled the town.

But another, the Interior Minister, Gaetan Kakudji, said that fighting was still going on.

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Mr Kakudji said the rebel soldiers are mainly ethnic Tutsis backed by troops from neighbouring Rwanda were holding part of the town, which is on the border with Rwanda.

"The Banyamulenge (ethnic Tutsis) backed by Rwandan troops are in one part of the town while our forces control another," Mr Kakudji said.

A Bukavu resident said the fighting began early on Tuesday with heavy bombardment. He said it was impossible to say who controlled the town.

United Nations sources also reported fighting overnight in the town of Uvira, 120 km (75 miles) south of Bukavu.

The government on Monday imposed a dusk-to-dawn curfew in Kinshasa, following sporadic gunbattles there. .

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Officials of the government of President Laurent Kabila accused Congolese Tutsi forces and Rwandan troops of starting the violence. The government has urged its neighbours to resist the temptation to involve themselves in an army rebellion.

However, a Rwandan military spokesman has denied there were any Rwandan soldiers in the country.

'Withdrawing support'

Earlier, the military commander of the Congolese Army in the eastern town of Bukavu said he and other army units in the east were withdrawing their support from Mr Kabila's government, accusing him of driving the country on a downward slope.

Witnesses said the border between Congo and neighbouring Rwanda was closed because of fighting involving the Congolese armed forces and ethnic Tutsis of the Banyamulenge group.

Soldiers in three towns - Goma, Bukavu and Kindu - are said to be involved in the uprising.

In Kinshasa, rival soldiers clashed in a military barracks and a nearby base, both of which have been sealed off by government troops.

The BBC correspondent in Kinshasa, William Wallace, says it remains unclear whether the fighting in the capital has been provoked by heightened tensions within the military or by a serious bid by dissidents to take power.

The unrest follows President Kabila's decision last week to order Rwandan troops to leave the former Zaire.

Rwanda's Tutsi-dominated army helped spearhead the seven-month bush war that brought Kabila to power in May 1997.