More than 3.5 million children are at risk of water-borne diseases in Pakistan following the worst flooding in the county's history, the UN says.
There is a severe shortage of clean water and children are at risk of diseases such as watery diarrhea, dysentery and cholera.
UN Secretary-General Ban Ki-moon flew over the flood-ravaged area Sunday and said he had never seen such a wide-scale disaster.
The UN has appealed to the international community for $460-million in relief, of which 60 per cent has already been collected.
The floods began two weeks ago and some 20 million people and 160,000 kilometres of land -- about one-fifth of the entire country -- have been affected.
At least 1,500 people have died in the flooding.
Disaster assistance has been slow and there is a threat of civil disturbances.
Pakistani flood survivors blocked a highway Monday to protest the slow delivery of aid.
Angry victims said they were being treated like animals and the government was only handing out food when the media was present. Hundreds of victims blocked a major highway with stones and garbage in protest.
"They are throwing packets of food to us like we are dogs. They are making people fight for these packets," protestor Kalu Mangiani said.
Reporting from a clinic in Nowshera, Pakistan, NBC's Stephanie Gosk said conditions are worsening.
"We were surprised by how bad it is. We were at a clinic where there were three children to a bed, the doctors told us they had completely run out of antibiotics and other medicine that they need to treat these kids," she told CTV's Canada AM Monday morning. "There are real fears that their symptoms are those of cholera. They don't have the money or time to test them.
"We didn't see any indication of any international relief efforts."
Dave Toycen of World Vision Canada said his organization had workers on the ground in Pakistan before the flooding began, and they were able to distribute food and water almost immediately.
But he said far more aid and relief workers are needed on the ground to stave off a looming humanitarian disaster.
"The under twos and the elderly, that's what we're worried about now," Toycen told Â鶹´«Ã½ Channel Monday night. "With diarrhea, there's been one case of cholera, we're just worried deeply about where this could lead in terms of death and illness."
There are also worries that the flooding could destabilize the country further, which would be another blow to the U.S.'s hopes of defeating the Taliban and al Qaeda in Pakistan.
