Devastating rains in Pakistan killed at least 21 people overnight, destroying crops and houses in the flood-prone south of the country, a government official said Friday.

"At least 21 people died, most of them because of falling roofs during rains on Thursday night," said Sajjad Haider Shah, an official at the disaster management authority in the southern province of Sindh.

Fifteen of the deaths occurred in the Mirpurkhas district, which was worst-affected, he told AFP.

"The rains have also destroyed crops and forced hundreds of people to leave their homes," said Shah.

The meteorological office forecast more rain this week.

Last year, the worst floods in Pakistani history affected 21 million people and killed another 1,750. Charities accuse Pakistan of since failing to invest in prevention measures.