At least 20 people died and a further 60 were feared dead after a boat capsized in eastern Democratic Republic of Congo, Red Cross and United Nations officials said on Thursday.

UN peacekeepers and local authorities were still searching for survivors after the boat, carrying about 120 people on a river in the eastern province of Maniema, tipped over on Wednesday.

"A longboat capsized and 20 people drowned," Jacques Katshishi, secretary general of the Congolese Red Cross, told Reuters, without giving any further details.

A spokesman for the UN peacekeeping mission in Congo confirmed the boat accident. "It was yesterday. It is thought that there could be around 80 dead. There were around 120 people on board," said spokesman Madnodje Mounoubai.

Congo's roads and railways are in tatters after decades of neglect, so people are forced to use a network of rivers to travel around the vast central African nation.

No reason was given for Wednesday's accident, though overloading is often blamed.