"Everything I saw and heard today confirmed that this disaster -- already one of the largest the world has seen -- is still getting bigger," U.N. Undersecretary-General for Humanitarian Affairs and Emergency Relief Coordinator Valerie Amos said Wednesday.
She is on a 3-day tour of the province of Sindh, where more than 16,750 square miles are under water and nearly half a million homes have been destroyed.
The United Nations says that the death toll in Pakistan from the floods, which began at the end of July, stands at more than 1,750 and more than 1.8 million houses are categorized as either damaged or destroyed.
"With 21 million people affected across Pakistan this cannot be treated as just another crisis -- it is an immense and still unfolding catastrophe," said Amos in a statement.
Just during the last few days, 40 villages in Sindh were flooded, said Amjad Jamal of the World Food Program, IRIN, the news service of the U.N. Office for the Coordination of Humanitarian Affairs reports.
Also severely affected are the provinces of Khyber Pakhtunkhwa, Punjab and Balochistan.
"The concerns people expressed to me were mostly about problems we can address such as malaria, their children not getting enough to eat, skin diseases and insufficient shelter," Amos said. "People are also worried about their futures. For many of them, even when the waters recede, they will have nothing to go back to."
There are still scores of marooned villages across Pakistan where no assistance has been received in more than a month, IRIN reports. Relief agencies attribute the void to a combination of geography, the tremendous scale of the disaster and the play of local politics.
Out of the 8.5 million people identified to be in need of shelter in Pakistan, 1.3 million have been helped so far, said Saleem Rehmat of the International Organization for Migration.
"Access and resources, including manpower, remain a huge issue," he said.
So far $294 million -- 64 percent -- of the $460 million requested by the United Nations and its partners for the Pakistan initial flood emergency response plan has been received.
"The humanitarian community has so much to offer here. We can prevent a lot of needless suffering but only if our operations on the ground are scaled up properly. I am going to have to ask our supporters to dig deeper as we need a lot more resources," Amos said.