At least 51 people have died across the impoverished province of Baluchistan and Prime Minister Raja Parvez Ashraf on Sunday declared three districts as calamity-hit areas.

He announced assistance worth 2,600 million rupees ($27.5 million) for relief and rehabilitation work in the province where a torrential monsoon spell this month smashed a 30-year record, they said.

Heavy rains lashed the province for 32 hours on September 11 and the meteorological department recorded 432 millimetres (17 inches) of rain, head of the provincial disaster management authority Akbar Durrani told AFP.

Officials released the figures almost two weeks after the rains hit the sparsely populated province, which is struggling with a separatist insurgency and Islamist militants.

Flash floods damaged crops over 380,000 acres (155,000 hectares) of land in 13 districts, he said adding that the worst hit were Jaffarabad, Naseerabad and Jhal Magsi, where a large area remains submerged.

At least 22 people have died in Naseerabad alone and eight in Jafffarabad, Durrani said. The remaining casualties were reported elsewhere in the province.

Another 115 people were injured in the rains which also killed 1,778 cattle.

Around 700,000 people have been affected, many people suffered crop and property losses, Durrani said.

"We have already distributed 6,670 tents and 2,378 metric tons of food items, while the prime minister promised to immediately rush 20,000 more tents," he said.

The government has set up several medical camps where treatment has been offered to nearly 3,000 people suffering gastrointestinal diseases and more than 2,500 cases of malaria.

"We have not launched any appeal for foreign assistance. We are so far relying on own resources and we hope we can handle the situation," Durrani said.

He stressed the rescue work is over and rehabilitation work including repair of roads and infrastructure has started.

He said the level of disaster was much less than 2010, when unprecedented monsoon rains triggered catastrophic flooding across the country, killing almost 1,800 people and affecting 21 million.