The flooding came after a week in which the heaviest rain and snowfall in years has caused scores of deaths. Neighbouring India has also suffered from flooding, avalanches, mudslides and house collapses.
At Pasni, near the coast of Pakistan's Baluchistan province, at least five villages, with a total of 7,000 inhabitants, were submerged when the Shadikor dam burst under the strain of the rainfall. Witnesses described seeing lorries and people being swept out to the Arabian sea.
At least 10 people were killed when the bus they were travelling on was swept away by the waters. Twenty other passengers managed to struggle out of the bus to safety. Thousands of troops have joined rescue operations in the remote region.
Such heavy rain is unheard of in Baluchistan, normally an arid desert. The dam was built in an effort to help irrigate the parched landscape.
Local authorities said more than 1,200 people had been pulled alive from the waters, but more than 400 were still unaccounted for. Fifty-four bodies were found, most of them by coastguards trawling the coast with fishing nets.
"The army has started rescue operations to try to save as many lives as possible," said the provincial cabinet minister, Sher Jan Baluch.
Thousands of Pakistani troops have been deployed in an effort to save survivors, but rescue efforts were being hindered by further heavy rains last night.
There were hopes that survivors may be sheltering in neighbouring villages or the nearby mountains. Some of those who were found alive had climbed into trees to escape the water. Troops diverted the floodwaters to save other nearby towns.
The past week has seen Pakistan's heaviest rain and snowfall for 16 years. At least 37 people have died in other parts of the country. Parts of the mountainous north have been completely cut off, with roads snowed under and flights cancelled because of the bad weather. In neighbouring India, more than 10ft of snow has fallen in just a few days. At least 3,000 people have been stranded on a mountain highway for five days. Motorists and bus passengers were stranded in dangerously cold conditions after the road was blocked by snowslides.
"Security forces and local villagers are providing food and shelter to the stranded passengers," a government spokesman said.
In both Pakistan and neighbouring India the extreme weather has also led to deaths from avalanches. Soldiers on both sides of the line of control dividing Kashmir have died. Six Indian soldiers were killed yesterday when avalanches swept away their bunkers, while two soldiers were killed in an avalanche on the Pakistani side on Thursday.
Baluchistan, the scene of yesterday's dam burst, is one of the wildest and most unruly places in Pakistan. Most of the province is subject to tribal law, and security is not in the hands of the police.
There has also been serious unrest in recent weeks.The country's gas supplies were cut off when Baluch tribesmen attacked an oil refinery at Sui. The attacks followed rumours that a Baluch woman had been raped by soldiers.