"People are saying it's dangerous to stay," Riaz Hussain, local resident, said as he finished packing his family and possessions, including two water buffalo, onto a trailer behind a tractor.

"I'll find some corner to live with my family."

'Race against time'

On Sunday Pakistan said donors from around the world had pledged more than $800m, almost twice the amount the UN had orginally sought when the crisis hit.

The floods have already affected about one-fifth of Pakistan's territory, straining its civilian government. At least six million people have been made homeless and 20 million affected overall.

"We have already provided shelter for a million people and ordered shelter for a further 2.4 million, which is in the pipeline," Maurizio Giuliano, a spokesman for the UN Office for the Co-ordination of Humanitarian Affairs (OCHA) in Islamabad, told the AFP news agency.

SPECIAL COVERAGE

"We have more than doubled the rate at which we are delivering relief but, since August 11, the number of people who need emergency help has undoubtedly more than tripled. We are in a race against time."

Aid groups have been trying to help the government by providing food, medicine, shelter and other crucial assistance, but poor weather, the destruction of roads and bridges, as well as the sheer scale of the disaster have hindered distribution.

At a relief camp in the Sukkur area, some victims said it was difficult to get the food aid even when it did arrive.

"I am a widow, and my children are too young to get food because of the chaos and rush," Parveen Roshan told The Associated Press news agency.

"How can weak women win a fight with men to get food?"

The Financial Tracking Service (FTS), a UN database that aims to track all donations, showed late on Friday that $490.7m in funding had been collected, with another $325m pledged.

Just over half of the money raised for Pakistan has come from the UN's emergency appeal fund launched on August 11, while the rest came via bilateral aid, chiefly from Saudi Arabia, as well as from charities, private organisations and companies.

The United Nations said it needs at least 40 more helicopters to reach the large number of people cut off by the flooding.