A rebel commander, General Celestin Ilunga, said a military plane dropped four or five bombs on the rebel capital, Goma, and subsequently attacked the town of Uvira, 200km further south.

Other rebel sources said 28 people had been killed and a further 15 injured in the Goma attack, which began at 1900 local time (1700 GMT).

There are no casualty figures for the attack on Uvira.

The bombings are the first attacks by government forces on the two rebel strongholds.

'Act of desperation'

General Ilunga described the attacks as an act of desperation by President Laurent Kabila in the face of increasing territorial gains by the rebels during the nine-month-old civil war.

He said the bombing appeared to be in response to recent rebel gains in southern Congo, where his troops captured Kabila's hometown of Manono, and Bene Dibele, outside the diamond center of Mbuji-Mayi.

General Ilunga said the rebels had killed at least 50 government troops during the fighting in the south, and captured military vehicles and ammunition.

Birthplace of rebellion

Congo's easternmost region, bordering on Rwanda and Burundi, was where the rebellion against President Kabila's government began, led by the Banyamulenge - the ethnic Tutsis who had previously helped Mr Kabila to wrest power from former President Mobuto Sese Seko.

The rebels now accuse the president of mismanaging the country, and of pursing a policy of ethnic discrimination against them.

The conflict has had wide regional repercussions, with Zimbabwe, Namibia, Angola and Chad sending troops to support President Kabila, while Uganda, Rwanda and Burundi have backed the rebels.