MINGORA, PAKISTAN (AFP, REUTERS) - Army helicopters flew sorties over cut-off areas in Pakistan's mountainous north on Wednesday (Aug 31) and rescue parties fanned out across waterlogged plains in the south as misery mounted for millions trapped by the worst floods in the country's history.

Monsoon rains have submerged a third of Pakistan, claiming at least 1,160 lives since June and unleashing powerful floods that have washed away swathes of vital crops and damaged or destroyed more than a million homes.

United Nations chief Antonio Guterres called it "a monsoon on steroids" as he launched an international appeal late Tuesday for US$160 million (S$220 million) in emergency funding.

Officials say more than 33 million people are affected - one in every seven Pakistanis - and it will cost more than US$10 billion to rebuild.

The focus for now, however, is reaching tens of thousands still stranded on hills and in valleys in the north, as well as remote villages in the south and west.

"We appeal to the government to help end our miseries at the soonest," said Mohammad Safar, 38, outside his submerged home on Wednesday in Shikarpur in the southeastern province of Sindh.

"The water must be drained out from here immediately so we can go back to our homes." There is so much water however that there is nowhere for it to drain.

Climate Change Minister Sherry Rehman described the country as "like a fully soaked sponge", incapable of absorbing any more rain.

'Burning with pain'

Pakistan has received twice its usual monsoon rainfall, weather authorities say, but Balochistan and Sindh provinces have seen more than four times the average of the last three decades.

Padidan, a small town in Sindh, has been drenched with an astonishing 1.75 metres since June.

Pakistan receives heavy - often destructive - rains during its annual monsoon season, which are crucial for agriculture and water supplies, but such intense downpours have not been seen for three decades.

Officials have blamed climate change, which is increasing the frequency and intensity of extreme weather around the world.

Earlier this year much of the nation was in the grip of a drought and heatwave, with temperatures hitting 51 deg C in Sindh province.

Plea to open India route 

International aid agencies struggling to help hundreds of thousands of people displaced by deadly floods in Pakistan have asked for the easing of curbs on imports of food from Pakistan’s old rival India, a Pakistani minister said on Wednesday.

Pakistan faces surging food prices, compounding the misery for the millions affected by the disaster.

Finance Minister Miftah Ismail said the government was considering loosening restrictions on the largely closed border with India to let in supplies of vegetables and other food.

“More than one international agency has approached the government to allow them to bring food items from India through the land border,” Ismail said on Twitter.

He said the government will decide whether to allow that based on supply conditions and after consulting its coalition partners and key stakeholders.

Prime Minister Shehbaz Sharif said that hundreds of thousands acres of crops have been washed away.

“We have lost rice crop. Fruits and vegetables have been destroyed,” he told reporters after his trip to the flooded areas in the north.

General Akhtar Nawaz, chief of the national disaster agency, has said more than two million acres of agricultural land were flooded.

The nuclear-armed neighbours have fought three wars since they were carved out of British India in 1947 and their border is heavily fortified and largely sealed off.

Very little trade and travel takes place between Muslim Pakistan and predominantly Hindu India despite historic, cultural and family ties.

The latest disaster could not have come at a worse time for Pakistan, where the economy is in free fall.

Pakistan Prime Minister Shehbaz Sharif promised aid donors that any funding would be responsibly spent.

"I want to give my solemn pledge and solemn commitment... every penny will be spent in a very transparent fashion. Every penny will reach the needy," he said.

Pakistan was already desperate for international support and the floods have compounded the challenge.

Prices of basic goods - particularly onions, tomatoes and chickpeas - are soaring as vendors bemoan a lack of supplies from the flooded breadbasket provinces of Sindh and Punjab.

Makeshift relief camps have sprung up all over Pakistan - in schools, on motorways and in military bases.

Displaced people are sweltering in the summer heat with sporadic food aid and little access to water.

In Sindh, doctors treated patients who made their way to a makeshift clinic after walking barefoot through dirty floodwater, mud and streets full of debris and manure.

"My child's foot is burning with pain. My feet too," said Ms Azra Bhambro, a 23-year-old woman who had come to the clinic for help.

In the northwestern town of Nowshera, a technical college was turned into a shelter for up to 2,500 flood victims.

The army said its helicopters had flown over 140 sorties in the past 24 hours, plucking people from cut-off areas in the north, and dropping off food and fresh water elsewhere.

Aid flights have arrived in recent days from China, Turkey and the United Arab Emirates, while other countries including Canada, Australia and Japan have also pledged assistance.