Floods in Afghanistan's Kandahar kill at least 20

Flash floods have engulfed up to 2,000 homes in southern Afghanistan, killing at least 20 people.

Flash floods in Kandahar, Afghanistan have killed at least 20 people, including children. (AAP)

At least 20 people including children have been killed in southern Afghanistan by flash floods that engulfed up to 2,000 homes and swept away cars, the UN agency co-ordinating relief efforts says.

Heavy rains struck Kandahar city and six districts on Friday, the UN Office for the Co-ordination of Humanitarian Affairs (OCHA) said in a statement on Saturday.

Afghan government officials said hundreds of houses in Herat province were destroyed in flash floods.

A man stands next to a home that was damaged in heavy rains in Kandahar, Afghanistan, 02 March 2019. Source: AAP

Flood-affected families have been evacuated to secure areas in the districts and Kandahar city, including schools, mosques and government buildings.

At least 10 people, including children, were missing in Arghandab, Daman, Spin Boldak and Dand districts.

The OCHA statement said a large number of Kochi (nomadic) families, about 500 people, were stranded on the river bank and there was an urgent need for air support to rescue them.

The rugged mountainous terrain, heavy snowfall and lack of roads were retarding the pace of immediate relief and rescue operations, said a senior official working for the Afghanistan Natural Disaster Management Authority in Kabul.