The floods, triggered by torrential monsoon downpours, have engulfed Pakistan's Indus river basin, killing more than 1,600 people, forcing two million from their homes and disrupting the lives of 14 million people, or 8 percent of the population.

At a hospital in Mingora, the main town in Swat valley, an official who asked not to be named told Reuters one case of cholera was confirmed. A German humanitarian organization said there were also six suspected cases there. An epidemic could create another disaster for Pakistan.

The United Nations is worried about water-borne diseases. There have been 36,000 suspected cases of potentially fatal acute watery diarrhea reported so far. It says the floods have affected about one-third of Pakistan.

Floods have roared down from the northwest to Punjab province to southern Sindh.UN Secretary-General Ban Ki-moon is expected to visit Pakistan over the weekend to discuss the crisis.

Meanwhile, Pakistan's president Asif Ali Zardari has directed that there should be no official celebrations of Independence Day on August 14 as the country tries to cope with devastating floods.

Asif Ali Zardari will instead spend the day touring affected regions in Khyber Pakhtunkhwa and Punjab provinces.