Islamabad: UN chief Ban Ki-moon praised the global community as emergency donations for Pakistan neared 500 million dollars, but warned the flood-stricken nation faces "years of need".
The Financial Tracking Service (FTS), a UN database that aims to track all donations, showed late Friday that 490.7 million dollars in funding had been collected, with another 325 million dollars pledged.
The United States has given the most, followed by Saudi Arabia and Britain.
The United Nations led a meeting on Thursday to rally support for Pakistan -- hit by a disaster which Ban described as a "slow-motion tsunami".
On Friday Ban welcomed the donations, but warned: "We must keep it up. Pakistan is facing weeks, months and years of need."
The floods have killed 1,500 people in the nuclear-armed country of 167 million -- which is a US foreign policy priority on the frontline of the struggle against Al-Qaeda-linked extremists.
On Saturday, six flood victims, including three women and two children, were killed and 25 others injured after being electrocuted in the Kashmore district of southern Sindh province, officials said.
"They were killed when a 11,000 kilowatt main transmission electricity line fell on the tractor-trolley in which they were travelling," Abid Shah, the administrative chief of Kashmore district, told a news agency by telephone.
Police in the area also confirmed the incident.
Pakistan`s weak, democratically elected government has faced an outpouring of public fury over sluggish relief efforts, and there are growing fears that losses of up to 43 billion dollars could bring economic ruin.
The International Monetary Fund said it would meet Pakistani officials in Washington next week to discuss ways of helping ease the impact of the floods on the nation`s economy.
Reports suggest Pakistan may ask the IMF to ease the terms of a 10-billion-dollar loan it received in 2008.
Eight million flood survivors in desperate need of food, shelter and clean drinking water require humanitarian assistance to survive, as concerns grow over potential cholera, typhoid and hepatitis outbreaks.
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.
According to the FTS, 263 million dollars has been donated via the UN appeal -- 57 percent of its target -- with the lion`s share of that total, 88 million, coming from the United States.
Britain has donated 34.7 million via the UN fund while Australia has given 26.6 million and the European Commission 18.6 million.
"It is very likely that the need for donations will strongly increase because... the number of people in need of immediate humanitarian aid has risen from six to eight million," Maurizio Giuliano, spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA) in Islamabad, said.
The UN increased its estimate of the number of people without shelter from two million to six million in the first 10 days, he added.
"We have already provided shelter for a million people and ordered shelter for a further 2.4 million, which is in the pipeline," he said.
"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."
The UN World Food Programme said it urgently needs helicopters to get food to millions of flood victims who remain cut off by the high waters, although weather forecasters say the monsoon systems are easing off.
The agency warned that the floods have killed or are threatening millions of livestock, and launched an urgent appeal for animal feed.
The Pakistani-American community has urged Washington to adopt a proposal to give preferential access to Pakistan`s textiles, hit hard by the floods, and forgive a 1.5 billion dollar loan.