Survivors crammed into inadequate shelters expressed anger over inaction from the Pakistani government on Monday as the death toll from the country's worst floods in generations topped 1,100.
UN chief Ban Ki-moon pledged extra aid of up to 10 million dollars to help in the crisis, which local officials say has affected more than 1.5 million people in Pakistan's northwest province of Khyber Pakhtunkhwa.
"I had built a two-room house on the outskirts of Peshawar with my hard-earned money but I lost it in the floods," said labourer Ejaz Khan, one of several hundred people who demonstrated in the northwestern city of Peshawar.
"The government is not helping us... the school building where I sheltered is packed with people, with no adequate arrangement for food and medicine," the 53-year-old said.
The floods and landslides triggered by monsoon rains capped a devastating week in Pakistan, where 152 people were killed when an Airblue passenger jet slammed into hills overlooking the capital in the country's worst plane crash.
Ban said he was "deeply saddened" by the losses incurred in the worst floods in Pakistan for 80 years, reiterating a full commitment to "meeting the humanitarian needs" of those affected.
Pakistani television footage and photographs taken from helicopters showed people clinging to the walls and rooftops of damaged houses as water rushed through villages, with waterborne diseases emerging as a threat to survivors.
Thousands of homes and vast swathes of farmland have been destroyed in a region of Pakistan reeling from years of extremist bloodshed.
"The floods have killed more than 1,100 people in different parts of Khyber Pakhtunkhwa and affected over 1.5 million," said Mian Iftikhar Hussain, the northwest province's information minister.
"We are receiving information about the loss of life and property caused by the floods all over the province," he said, adding that he feared the death toll could rise.
A senior official at the provincial Disaster Management Authority (PDMA) confirmed the toll.
Hussain said more than 3,700 homes had been swept away and the number of people made homeless was mounting.
Hundreds of survivors sought shelter in schools in Peshawar, the main city in northwest Pakistan, and in Muzaffarabad, the capital of Pakistani Kashmir, after escaping the floods with children on their backs.
Pakistan's meterological office said the northwest had been hit by an "unprecedented" 312 millimetres (12 inches) of rain in 36 hours.
The US government announced an initial 10-million-dollar aid pledge and has rushed helicopters and boats to Pakistan.
China, which has also been hit by severe flooding, announced a 10 million yuan (1.5 million dollar) donation, according to the official Xinhua news agency, which cited a government website.
Hussain said rescue teams were trying to reach 1,500 tourists stranded in Swat district, the scene of a major anti-Taliban military offensive last year.
"We are also getting confirmation of reports about an outbreak of cholera in some areas of Swat," he said.
The Pakistan Air Force said it had airlifted more than 500 stranded people, including six foreigners, as part of relief operations and was carrying out reconnaissance missions to assess the damage to infrastructure.
President Asif Ali Zardari is due in Paris on Monday for a two-day visit, and French Foreign Minister Bernard Kouchner expressed France's "solidarity" with Pakistan in the face of the floods.
Floods also ravaged parts of Afghanistan, killing at least 65 people and affecting more than 1,000 families, officials said.