One witness, who escaped the deluges in Buner, described seeing floodwaters carrying hundreds of boulders and "tonnes of rocks" crashing down.
Pakistan has received higher-than-normal monsoon rainfall in 2025, which experts link to climate change, triggering floods and mudslides that have killed some 541 people since June 26, according to the National Disaster Management Authority.
Hundreds of rescue workers are still searching for survivors in Buner, one of several places in Khyber Pakhtunkhwa province where torrential rains and cloudbursts caused massive flooding on Friday, said Mohammad Suhail, a spokesman for the emergency services.
Dozens of homes were swept away.
First responders have been trying to recover bodies from the worst-hit villages of Pir Baba and Malik Pura, where most of the fatalities were, said Kashif Qayyum, a deputy commissioner in Buner.
Police officer Imtiaz Khan, who narrowly escaped the deluges, said floodwaters carrying hundreds of boulders struck and flattened homes within minutes.
"A stream near Pir Baba village in Buner swelled without warning," Khan told The Associated Press.
"At first, we thought it was a normal flash flood, but when tonnes of rocks came crashing down with the water, 60 to 70 houses were swept away in moments," he said, adding that many bodies were left mutilated.
"Our police station was washed away too and if we hadn't climbed to higher ground, we would not have survived."
Rescuers said they saw large swathes of Pir Baba village destroyed, wrecked homes, and giant rocks filling the streets as the water started to recede.
Most victims died before reaching the hospital, said Mohammad Tariq, a doctor in Buner.
"Many among the dead were children and men, while women were away in the hills collecting firewood and grazing cattle," he said.
Mourners attended mass funerals on Saturday, while authorities supplied tents and food items to flood-affected people in Buner.
Local cleric Mufti Fazal said he led funeral prayers at multiple locations since Friday morning.
"Before yesterday's floods, the area was bustling with life.
"Now, there is grief and sorrow everywhere."
Schoolteacher Suleman Khan lost 25 members of his extended family, saying he and his brother survived only because they were away from home when the floods hit his village Qadar Nagar.
According to the provincial disaster management authority, at least 351 people have died in rain-related incidents this week across Khyber Pakhtunkhwa and the northern region of Gilgit-Baltistan.
Nearly 300km away in Indian-controlled Kashmir, rescuers scoured the remote village of Chositi in the district of Kishtwar on Saturday, looking for dozens of missing people after it was hit by flash floods two days ago, killing 60 and injuring some 150, about 50 in critical condition.
Thursday's floods struck during an annual Hindu pilgrimage in the area.
Authorities have rescued more than 300 people, while some 4000 pilgrims have been moved to safety.
Such cloudbursts are increasingly common in India's Himalayan regions and Pakistan's northern areas, and experts have said climate change is a contributing factor.
Pakistani officials said rescuers since Thursday have evacuated more than 3500 tourists trapped in flood-hit areas across the country.
Many travellers have ignored government warnings about avoiding vulnerable regions in the north and northwest.
Pakistan witnessed its worst-ever monsoon season in 2022.
It killed more than 1700 people and caused an estimated $A61 billion in damage.
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