Bujumbura - Fifty rebels were killed in Burundi this week when the navy sank a boat they were travelling in on Lake Tanganyika, a military source said on Friday.

The incident took place at dawn on Wednesday near the port town of Nyanza-lac in southwest Burundi, army spokesman Colonel Augustin Nzabampema said.

"A military vessel attacked two rebel boats, one was sunk with the crew and rebels it was carrying, while the second managed to escape to Ubwari, a lake island in the Democratic Republic of Congo," explained the spokesman.

The island is allegedly used as a haven by Burundian rebels of the Forces for the Defence of Democracy.

Fishing has been banned since Wednesday in Burundian waters of the lake for "security reasons".

"Rebels were stepping up attacks on civilian boats, they even attacked a Tanzanian boat," the spokesman said.

"It is hard to tell the fishing boats from the rebel boats," he added.

A civil war has raged in Burundi since 1993, pitting armed Hutu groups against a government and army dominated by the small Tutsi minority. - Sapa-AFP