Flash floods triggered by torrential rains in northern Afghanistan killed at least 19 people and left thousands homeless, an official said on Sunday.

Another 56 people were missing after the flood hit on Saturday in Sayyad and Share Naw districts of Sari Pul province, the provincial governor Abdul Jabar Haqbeen told AFP.

"More than a thousand families have been affected and a thousand homes destroyed," he said, adding that rescuers were in the area, backed by Afghan and NATO air support.

"Around 6,000 people who had taken shelter in mosques and schools have been moved to safer places," he said.

Afghanistan's harshest winter in 15 years saw unusually heavy snowfalls and experts predicted that rivers swollen by melting snow were likely to flood in the mountainous north in spring.

According to IMMAP, a data-analysis and mapping company, 15 percent of Afghanistan's population is at high risk of being affected.

In March, the UN humanitarian office for Afghanistan said at least 145 people were missing and "presumed dead" after an avalanche hit a remote village in northeastern Badakhshan province.