The information comes from the rebel group Sudan Liberation Movement/Army (SLM), which controls the mountainous area of Jebel Marra in Darfur where the affected village of Tarasin is located.
After several days of rain, the landslide occurred on August 31.
"Preliminary information indicates that all villagers, estimated to be more than a thousand individuals, have perished, with only one survivor," it says in a statement from the SLM.
They are now appealing to the UN and other aid organizations for help in recovering the dead who are buried under earth and debris.
Sudan is embroiled in a bloody civil war between the army and the paramilitary Rapid Support Forces (RSF), which has plunged the country into one of the world's worst humanitarian crises.
In war-torn Darfur, the fighting has escalated since the army regained control of the capital Khartoum in March. Famine prevails in parts of the region, and the situation in Sudan is often described as the world's largest humanitarian crisis.
The SLM has largely remained neutral during the civil war, but parts of the rebel group have recently joined the army's fight to combat the RSF.
