"There are 74 bodies in the morgue at Kisangani general hospital, of which 28 were brought in this morning," the organisation's Congolese secretary general Mario-Real Shutsha told AFP.
Earlier in the day, Hewa Bora Airways director Stavros Papaioannoua said there were 56 confirmed deaths and warned the toll may rise further.
The Boeing 727 operated by Hewa Bora crashed at Kisangani airport yesterday as it attempted to land in heavy rain with 112 passengers and six crew onboard.
The plane was on its regular commercial route from Kinshasa to Kisangani and Goma when it hit the storm as it approached the airport, a local administration spokesman said.
Jean-Marc Mambimbi, a doctor in the Oriental province, said more than 40 people were still being treated for injuries.
Papaioannoua said Red Cross staff worked in difficult conditions until the early hours today to free the injured and remove bodies from the plane wreckage.
All three pilots and a mechanic were killed in the crash, he added.
Plane accidents frequently occur in DR Congo, often blamed on ageing and poorly maintained aircraft, the flouting of safety rules and bad weather.
Each of its 50 or so airlines has been blacklisted by the European Union.