More than six million people have been affected by the worst floods in Pakistan's history, according to the UN, which noted that thousands of people did not have access to aid as bad weather hampers relief efforts.
Islamabad puts the number of affected people between 12 to 14 million.
Meanwhile, the world body has said that Pakistan will need millions of dollars to get out of this crisis and in the long-term funding running into billions may be required for reconstruction.
"Things will probably get worse, before they start getting better," Martin Mogwanja, UN Humanitarian Coordinator in Pakistan said adding, "We are working at full speed to respond to the most urgent needs of the affected populations."
The floods have hit provinces of Khyber Pakhtunkhwa, Punjab, southern Sindh province. In Sindh, hundreds of villages have been flooded, and heavy showers are expected for the next three days.
"While comprehensive estimates are not yet available, it is certain that hundreds of thousands, if not millions, are being affected in this province," said Dennis Bruhn, a UN disaster management expert, according to the UN News Centre.
Wolfgang Herbinger, Country Director of the UN World Food Programme, expressed concern that 600,000 people were cut off without aid in the north of Khyber Pakhtunkhwa.
"No helicopter deliveries have been possible for three days because of bad weather," said Herbinger, as quoted by the News Centre.
During his visit to flood hit areas, Pakistan's Prime Minister Yousuf Raza Gilani renewed his call for help from the international community.
"Millions of people have suffered and still there is more rain and further losses are feared. I appeal to the world to help us, we are doing what we can," Gilani said, as reported by the Pakistani media.
However, the prime minister dismissed accusations that the government was not doing enough to help the people and relief efforts had been badly handled.
"In fact, the government has done everything possible under its control," he said, as quoted by Voice of America. "Provincial governments, they are all doing their utmost. But it is [an] unprecedented flood, it is beyond imagination and it is beyond expectation."
Efforts are also are being stepped up to prevent the spread of water borne diseases especially diarrhoeal diseases and respiratory infection, according to the WHO.