Floods cut off 800,000 Pakistanis

About 800,000 people have been cut off by floods in Pakistan and are only reachable by air, the United Nations has said, adding that it needs at least 40 more helicopters to ferry aid to increasingly desperate people.

The appeal was an indication of the massive problems facing the relief effort in Pakistan more than three weeks after the floods hit the country, affecting more than 17 million people and raising concerns about possible social unrest and political instability.

"These unprecedented floods pose unprecedented logistical challenges, and this requires an extraordinary effort by the international community," said John Holmes, UN under-secretary-general for humanitarian affairs.

Earlier, Pakistani prime minister Yousuf Raza Gilani said hundreds of health facilities had been damaged and tens of thousands of medical workers displaced.

Meanwhile, the country's chief meteorologist warned that it would be two weeks until the Indus River - the focus of the flooding still sweeping through the country - returns to normal levels. Qamar-uz-Zaman Chaudhry said high tides in the Arabian Sea would slow the drainage of the Indus into it. Those tides, he said, will begin changing on 25 August.

The UN High Commissioner for Refugees estimates that about 700,000 Pakistanis have been forced into makeshift settlements in the southern province of Sindh alone. While there have been no major disease outbreaks, aid agencies are increasingly worried, saying contaminated water and a lack of proper sanitation are already causing a spike in medical problems in camps for the displaced.