Swat, in northwestern Pakistan, was hit the hardest by the floods which submerged extensive areas, brought down bridges and swept away entire villages.
Martin Mogwanja, the Unicef representative in Pakistan, told Al Jazeera that the number of people affected continues to increase as the floods spread to the south of the country.
"This massive amount of water is moving downstream through the Punjab and Baluchistan provinces, and also moving through the Sindh province, where embankments have been broken and water is moving into to low-lying areas," Mogwanja said.
Other relief agencies such as the World Health Organisation said they were rushing in medical kits to affected areas to deal with diarrhoea.
With infrastructure crippled and drinking water sources contaminated, there are growing fears about an imminent outbreak of disease.
Aid agencies and Pakistani government officials will meet on Tuesday to determine whether to make an urgent international appeal for help.
Pakistan's National Disaster Management Authority said more than 29,500 houses were damaged and a key trade highway to China was blocked by the flooding.
"The entire infrastructure we built in the last 50 years has been destroyed," a spokesman for the provincial Disaster Management Authority in Khyber-Pakhtunkhwa said.
Al Jazeera's Sohail Rahman reported that aid agencies were having trouble reaching certain area's.
"The real problem is communication links and road links. You can’t get aid to places if you can’t the here," he said.
The floods have triggered heavy criticism of the government over its response to the disaster.
Red: Deeply affected
Yellow: Moderately affected
Brown: Flood warning issued
Around 300 people blocked a major road in the hard-hit Nowshera district to protest against receiving little or no aid, witnesses said.
"I think this is misplaced criticism. There is a deficiency [of aid] because of the magnitude of the calamity," Major General Athar Abbas of the Pakistani army told Al Jazeera.
"We are trying our best, taking into account our limited resources to reach out to a maximum amount of people in a maximum of areas," he said.
"Yes, there are certain areas which were left out, however, so far the rescue operation has been completed and we have gone into a major relief operation, providing provisions to the relief camps as well as medical assistance."
Many residents who lost their homes and livelihood also complain that they had not received any advance warning that raging waters were heading their way.
President Asif Ali Zardari's government is already unpopular over widespread allegations of corruption and its failure to tackle politically-explosive issues such as chronic power cuts.
Zardari is currently in Europe on a state visit.
Officials said it was too early to estimate the damage the floods had caused to the economy, but the rains had so far spared the main agricultural heartland in the Punjab.