The vessel is reported to have carried more than 400 people, of whom 170 have been saved while more than 200 are still missing.
Last month, at least 167 people died in two boat accidents on Lake Kivu.
The reason for this accident is unclear, but it is believed to have been overloaded with passengers.
DR Congo, which is about the size of mainland Western Europe, has a poor road network and many areas are inaccessible unless by air or boat – and the country’s only super-highway is the Congo River.
Recent boat accidents have prompted Félix Tshisekedi, who became president in January, to make it mandatory for passengers to wear life jackets.
It is unclear if the passengers on the boat that sank on Saturday evening from Inongo – the provincial capital of Mai-Ndombe Province – to Boliangwa wore life jackets.
(BBC)