NEW DELHI—Nepal needs $6.66 billion to rebuild infrastructure destroyed or damaged by the devastating earthquake in April and the aftershocks that followed, the country’s National Planning Commission said Saturday.

Economic fallout from the quake, which killed nearly 9,000 people and injured 22,000 others, has also pushed about 700,000 people below the poverty line in the Himalayan nation, which is one of the world’s least developed.

Govind Raj Pokharel, the planning commission’s vice chairman, said its damage estimates were based on surveys of 23 sectors of the economy, from agriculture to tourism and transport, which were affected by the disaster.

About 500,000 homes were rendered unusable by the quakes, leaving about three million people homeless. Many schools, government offices, bridges and roads were also badly damaged.

Nepal has invited more than 30 countries and more than two dozen aid agencies for an international conference on reconstruction that is to be held in Kathmandu later this month.