The rebels exchanged heavy gun and artillery fire with government troops during Sunday night.

Sporadic shooting could still be heard on Monday morning.

Rebels of the Hutu majority have stepped up attacks around Bujumbura since August, although this attack is believed to be the closest they have mounted.

The French news agency AFP quotes residents as saying that fighting broke out in the Mutanga district, less than five kilometres from central Bujumbura.

Casualties not known

The district was defended by government troops, a military source told AFP, and the heaviest exchanges lasted for about an hour. No details of casualties were available.

The rebels took up arms more than six years ago because of their opposition to power-sharing with ethnic Tutsis who dominate the armed forces.

More than 200,000 people are known to have died since the beginning of Burundi's civil war in 1993.

The latest round of peace talks aimed at ending the war ended last week without agreement.

Mediators in the Tanzanian town of Arusha were reported to have made significant progress although there were many key issues still to resolve.

The talks are expected to continue next month.