Burundi's army has driven rebels threatening the capital out of their strongholds in the Tenga Forest in heavy fighting, military sources said, but the rebel leader said they were still active.

The army killed five rebels of the National Liberation Forces (FNL) in a battle in the forest on Monday night, an army officer who asked not to be named told AFP.

"A group of about a dozen rebels fell into our hands, five were killed and the others escaped," he said. "There's still infiltration and even some rebel groups we haven't tracked down, but we're certainly established in Tenga."

Late Monday, the army said it had cleared the forest of the rebels, but FNL spokesman Anicet Ntawuhiganayo on Tuesday denied this, saying: "We're still in Tenga".

The forest has been "definitively liberated," senior army officer General-Major Samuel Gahiro said as he gave journalists in public service media a tour of the area, adjoining northern outskirts of Bujumbura.

"Measures will be taken to stop the rebels getting back into Tenga," added Gahiro, the commander of the central African country's 1st Military Region, a state radio report said late Monday.

The mainly Tutsi army launched an offensive late in November to flush out Hutu rebels of the FNL from the dense forest some six kilometres northeast of the capital.

On Monday, the army officially said 515 rebels and 28 soldiers had been killed and reported seizing 223 weapons and "a lot of ammunition".

But a military source, speaking anonymously, told AFP that in recent fighting, "about 100 soldiers were killed and several dozen were wounded, while the rebels took enormous losses.

"They had more than 350 killed and several hundred wounded, who they took to Gasarara and Mbare," their traditional regrouping areas.

Ntawuhiganayo said there was heavy fighting late Monday. The rebels lost 18 men and saw 24 wounded, and took 32 rifles, a machine-gun and a rocket-launcher from government forces, he said.

Prime Ndikumagenge, one of the local journalists allowed on the media tour, told AFP that "we were shown several places that we were told had been the hardest to take.

"We saw a lot of graves in different areas."

Other journalists in the group reported seeing "batteries of cannons, a multiple-rocket launcher" and "above all an impressive number of soldiers."