According to estimates, over 250,000 homes have been destroyed. Officials in the densely-populated southern province of Sindh have cautioned that major floods in the next 48 hours will threaten hundreds of communities along the Indus river.
"Basically, as we're hearing, the scale of the needs is absolutely daunting," said Melissa Fleming, a spokeswoman for the office of the UN High Commissioner for Refugees.
The World Food Programme (WFP) said it was preparing enough food aid for 2.5 million flood victims for three months, after delivering rations to 237,000 people in the worst-hit areas.
"It's a rolling emergency, this is something that's not over, the rains are continuing" said Emilia Casella for the UN food agency. "That means the people who are already affected are being further affected, and the people who weren't affected yet are now at risk of being hit by damage to their homes, their crops and their businesses.”
One million people hit by previous emergencies in the north-west of the country were already relying on WFP food rations before the latest disaster struck.
The WFP said it was likely to ask donors for about 63 million dollars to finance emergency aid in Pakistan, while Unicef appealed for 47.3 million dollars to fund its operations in Pakistan.