At least 17 people have been killed across Pakistan after heavy monsoon rains caused flooding and roofs to collapse, officials said.

More than 11 died in northwestern Khyber-Pakhtunkhwa province and six in southern Balochistan province on Saturday, the AFP news agency reported, citing disaster relief officials.

The deaths were caused by building collapses and electrocution, according to medical sources.

Heavy overnight rainfall in Karachi paralysed parts of the southern port city on Sunday morning. The rains, which started on Saturday, turned into a heavy downpour that inundated several areas of Pakistan's largest city.

"Houses were inundated, vehicles turned over, home furniture, utensils and pets swept away," said one Karachi resident, Mohammad Adnan.

"The situation is very bad. And there is no rescue. I have not seen [rescue teams]. They could not come as they haven't found a way to enter the affected areas," he added.

Another resident, Noor Ali, said some families were trapped in their homes and still waiting for rescue officials.

Others were seen being moved by tractors and trailers away from the flooded areas.

Forecasters have warned of more rains in Karachi and other parts of Pakistan.

Pakistan has suffered devastating monsoon floods for the last three years, including the worst in its history in 2010 when catastrophic inundations killed almost 1,800 people and affected 21 million.

Afghan flash floods

In neighbouring Afghanistan, meanwhile, at least 35 people were killed in flash floods in four eastern provinces early on Saturday, officials said.

The floods affected Nangarhar, Kabul, Khost and Nuristan provinces, with at least 13 reported dead in Kabul province and at least 17 in Nangarhar. As many as 50 people were said to be missing in a remote and mountainous area of Kabul, local police chief Shaghasi Ahmadi said.

Flash floods are common in these provinces, officials said.

Source: Agencies