HERAT: Flash floods have killed at least 32 people in western Afghanistan, destroyed homes and swept through makeshift shelters that housed displaced families, a government official said on Saturday.

Flooding caused by heavy rains started spreading on Thursday and left a trail of devastation across seven provinces, said Hasibullah Shir Khani, a spokesman for Afghanistan's National Disaster Management Authority.

Another 12 people were missing and more than 700 houses were destroyed or severely damaged, he added.

The floods worsen an already desperate situation. Hundreds of thousands of people were displaced in the region by last year's severe drought and the 17-year-long war with the Taliban.

Floods in early March caused further destruction and put this year's wheat harvest at risk.

"My house and my farmland have been destroyed by floods. If you go and see the destruction it makes you cry," said Shir Ahmad, who lives in a village in Herat province, which borders Iran.

Children waded through muddep floodwaters that flowed through tent camps for displaced people after the rain stopped. Some families strung salvageable clothes and bedding to dry.

Floods have destroyed hundreds of homes, some historic sites, thousands of acres of farmland, bridges and highways, said Jilani Farhad, a spokesman for the province.

Floods are a common occurrence in Afghanistan, although not usually this severe. The country has little infrastructure, such as ditches and sewers, to manage water run-off from rain or melting snow.

"There is huge destruction caused by floods," said Ahmad Jawed Nadem, head of refugees and repatriation for Herat. In one area, he said he saw more than 200 destroyed houses.

In Herat alone, eight people were killed, said Dr Abdul Hakim Tamana, head of public health for the province.

"They had the drought problem, and the floods and the conflict. They are very poor people and they lose all they have," the Afghan Red Crescent Society's secretary general Nilab Mobarez said.

"It’s not as simple as they will go on with their lives."

World Vision said it appeared tens of thousands of Afghans were affected. Some residents of Badghis province were calling it the worst storm in 20 years, it said.

Iran has also been flooded by torrential rains, overwhelming emergency services in some areas.