Thousands of rescuers were battling rain and knee-deep mud, digging homes out from under massive boulders in a desperate search for survivors.

"In Buner, at least 150 people are still missing. They could be trapped under the rubble of their homes or swept away by floodwaters," Asfandyar Khattak, head of Khyber Pakhtunkhwa's Provincial Disaster Management Authority, told AFP.

"Separately, in Shangla district, dozens of people are also reported missing," he added.

The ongoing rain was making rescue operations extremely difficult, Khattak said.

"There is no electricity or mobile signal in Buner, as power lines and mobile towers were damaged in the flash floods," he added.

In hardest-hit Buner district, at least 208 people were killed and "10 to 12 entire villages" partially buried, a provincial rescue spokesman told AFP.

"The operation to rescue people trapped under debris is ongoing," said Bilal Ahmed Faizi of the province's rescue agency.

He said around 2,000 rescue workers were engaged in recovering bodies from the debris and carrying out relief operations across nine districts, where rain was still hampering efforts.