More than 1,000 Pakistanis have died in monsoon-fed floods that left as much as 20 percent of the country under water. Though parts of the country are still flooded, humanitarian groups worry that water-borne illnesses could pose a long-term threat to Pakistanis.
Antonio Guterres, the U.N. High Commissioner for Refugees, said in a statement following a visit to the area that the level of destruction was unmatched.
"This is unprecedented," he said in a statement. "Nobody was prepared for such a level of destruction and for such difficult conditions for the people affected."
The U.N. Office for the Coordination of Humanitarian Affairs said more than 4.3 million people in Khyber Pakhtunkhwa, one of the worst-hit areas, are affected by the floods. More than 192,000 were left homeless.
The United Nations said it has received 67 percent of the $460 million sought for the initial relief effort in Pakistan.
"My hope is that the international community will understand the needs and fully correspond to the dramatic situation," said Guterres.