It was the latest in a series of maritime accidents in the sprawling country where people often travel on overloaded and unsafe vessels on the Congo, one of Africa's biggest rivers.
Sixty-one bodies had been recovered from the sinking during the night of Monday to Tuesday, and another 60 are believed to be missing, Nestor Magbado, a spokesman for the governor of the northwestern province of Mongala, told AFP.
He said there were 39 survivors.
With no manifest of the passengers on board, the number missing is an estimate based on the capacity of the boat, he said.
The vessel was actually nine traditional wooden canoes, known as pirogues, all tied together, Magbado said.
He added that the accident may have been caused by "overcrowding aggravated by bad weather" during the night.
The victims included hawkers and students travelling to the provincial capital Bumba, Magbado said. "There were all kinds of people".
The scale of the accident was not clear until it was reported by media late on Friday, and confirmed on Saturday by provincial authorities.
Magbado said the Mongala authorities had informed Kinshasa of the sinking just after it occurred, but had waited for more information about the number of casualties.
Search and rescue operations are continuing, but hopes are fading of finding more survivors, he said, adding that rescue efforts were hamstrung by the limited resources available to the authorities.
"We are struggling to make do with what we have," he said, adding that hopes of finding survivors were "fading with every passing day".
Provincial authorities have declared three days of mourning from Monday.
The vast country in central Africa, covering an area of 2.3 million square kilometres (900 million square miles), has very few passable roads and trips are often made on the Congo river and its tributaries as well as on the eastern lakes, Kivu and Tanganyika in particular.