The first quake, with a magnitude of 6.0 and its epicentre in Democratic Republic of Congo, happened at 10:30 a.m. (0730 GMT), followed by another 5.0 quake in densely populated southern Rwanda at 1:56 p.m. (1056 GMT).

"The death toll (in Rwanda) has risen to 33 people and up to 400 are seriously injured," Deputy Rwandan Police Chief Mary Gahonzire told Reuters. She said rescue efforts were underway.

The acting governor of Congo's South Kivu province, Bernard Watunakanza, told Reuters by telephone from the eastern town of Bukavu that aftershocks were happening "every 20 or 30 minutes".

"Up to now there are five dead and 149 seriously injured. Many people are traumatised," he said.

Witnesses to the Congo quake told of scenes of panic.

"It was a fear that I cannot even explain. We thought we were already dead," said Bukavu resident Jacqueline Hachez.

"We have never seen a quake like that here before. Part of my house is on the verge of falling into the lake (Kivu)."

An official from Congo's UN peacekeeping mission, known as MONUC, said buildings had been destroyed in Bukavu.

"There is lots of damage. Many buildings have been hit. Lots of houses have completely collapsed," said spokeswoman Jacqueline Chenard.

Earthquakes are common in the western Great Rift Valley -- a seismically active fault line straddling western Uganda, eastern Democratic Republic of Congo, Rwanda and neighbouring Tanzania.