The organisation reported that 98 percent of homes in quake-hit areas were either completely destroyed or severely damaged.
Taliban officials said the quake in Kunar province has killed 2,205 people and injured more than 3,640.
The Red Cross and the Afghan Red Crescent described the humanitarian situation in the affected areas as “extremely fragile and deteriorating,” warning of severe shortages of food, medicine and shelter.
Indrika Ratwatte, the UN’s humanitarian coordinator in Afghanistan, told Agence France-Presse the earthquake could affect hundreds of thousands of people.
Local rescue workers, operating with limited resources, are still trying to pull survivors from the rubble of collapsed homes, reports said. Landslides, rockfalls and blocked roads have left many villages cut off.
Alongside widespread destruction, poor weather and declining international aid are making the emergency response even harder.
Aid groups and humanitarian experts said the disaster should serve as a wake-up call to the international community.
An official from the Norwegian Refugee Council said Afghanistan cannot face such a catastrophe alone and urged the world to provide broad and sustained support.