The UN in Pakistan has described the humanitarian situation caused by the flood disaster as critical.
As flood waters continue to travel south through the country, tens of thousands of people are being displaced each day.
Earlier, the UN said it had raised some 70% of the money needed to provide emergency relief to flood victims.
The International Monetary Fund is to start talks with Pakistan later to discuss how to help with the crisis.
The IMF says the floods pose a "massive economic challenge" and it will review the country's budget and financial prospects.
The UN now estimates that the number of people who need basic shelter has gone from two million to six million.
Nearly 17 million people have been affected by the floods.
This week marks a month since the flooding started, and although the United Nations says it has raised close to 70% of the $460m (£295m) needed to provide emergency relief, many people have yet to receive any help, says the BBC's Jill McGivering in Sindh, the country's worst affected province.
Some $54m of that money is in uncommitted pledges. Resources available now total $263m.
In the UK, relief agencies have said public donors have given £29m ($45m) to the relief effort.
They also said the international response had been slow to build up, but that they had received more donations in the second week than the first week, which was rarely seen in such appeals.
Under threat
Tens of thousands of Pakistanis have fled a threatened flood surge, with the country's south now bearing the brunt.
An estimated four million people have now been displaced in the city of Sukkur alone.
A makeshift mud barrier, built by the army and volunteers, is Shahdadkot's last line of defence from the flood waters.
Flood defences around the southern town of Shahdadkot are still being strengthened - although most of the population have already left.
Provincial minister Mir Nadir Magsi told the BBC the situation remained critical in Shahdadkot, even though the river level had gone down.
The river water, which is being held back by a temporary barrier of mud and sand, is at a much higher level than the land. Bulldozers are mending small breaches in the barrier.
The threat appears to have receded from the city of Hyderabad, where the flood control barriers have held against what local officials said was a "super flood".
Evacuation activities, meanwhile, have started in Thatta district next to the Arabian Sea.
Dozens more villages have been inundated and although authorities expect flood waters to drain into the Arabian Sea over the next few days, evacuees who return may find their homes and livelihoods have been washed away.
Pakistan Prime Minister Yousuf Raza Gilani flew to the Gilgit Baltistan region in north-eastern Pakistan on Monday. Thousands of people are still trapped there in areas cut off from each other.
The region as a whole remains cut off due to the closure of the Karakoram highway, its only road link to the outside world.
The Pakistan government has said that the cost of rebuilding after the floods could be as high as $15bn (£10bn).
Overall, about 1,600 people have been killed and some 16.8 million affected, according to figures from the UN and Pakistani government.
