At least eight children were killed in floods that swept away houses in central and eastern Afghanistan this week, the United Nations' children's agency said on Tuesday, adding that more children were missing.

The United Nations is deploying response teams in eastern Afghanistan to provide aid to thousands of people who lost homes, livestock and crops in severe flash flooding that has hit the country since last week.

UNICEF's spokesperson in Afghanistan, Samantha Mort, said the child death toll could rise, and more children were missing and injured in the chaos wrecked by the floods.

Taliban administration disaster authorities have said at least 20 people were killed and appealed to the international community for help.

Afghanistan has been reeling from natural disasters this year, including a drought and a massive earthquake that killed over 1,000 people in June, with the nation largely cut off from the international financial system since the Taliban took over a year ago.

Flash floods kill 20 in eastern Afghan province

In rural areas, villages have been destroyed and thousands have lost their livestock and crops, exacerbating the country's hunger crisis. UNICEF aid workers said they were concerned over the risk of outbreaks of water-borne diseases such as cholera due to contaminated drinking water.

In the eastern city of Jalalabad, central urban areas were not spared destruction, UNICEF aid workers said. Water up to two metres high knocked down walls, destroyed belongings and left a thick layer of mud throughout inundated neighbourhoods.

"We can't emphasise enough how destructive the floods have been. … So much infrastructure has been affected, (including) schools. People have been repeatedly displaced, they're afraid to even go back to their old homes," said Veronica Houser, a UNICEF aid worker in Jalalabad.

One mother in Jalalabad lost three children after a torrent of water hit their house at night last week, causing it to collapse. Her two surviving children were showing signs of fear and distress, Houser said, adding that trauma among flood survivors was a concern and UNICEF had sent teams to provide mental health support to the worst-affected families.