Most of the dead are from a fishing community on Lake Albert.
Officials say the figure is based on the number of households buried after heavy rains caused parts of a nearby mountain to collapse.
Hopes of finding survivors has faded as rescuers do not have the means to move the large rocks.
"There are many people submerged whom we were unable to save," Pacifique Keta, the vice governor of Ituri province told Reuters news agency.
Mountains made the area difficult to access, Mr Keta added.
Many parts of west and central Africa are vulnerable to landslides, because land is heavily deforested and communities crowd into steep hillsides.
Eastern Congo is also on a seismic fault line and frequently suffers earthquakes.
More than 400 people have been killed and 600 remain missing after a similar disaster in Sierra Leone.
The death toll from Wednesday's landslide in north-eastern Democratic Republic of Congo is expected to rise above 200, officials say.