People are streaming back to Thatta, a historic city in southern Pakistan, where officials hope new levees hastily built from clay and stone will hold back water that inundated much of the country.

A flood victim carries a water bottle while taking refuge in a graveyard with her family in Thatta in Pakistan's Sindh province on Sunday. (Akhtar Soomro/Reuters)

Thousands who fled the water in neighbouring towns complained about the shortage of food and water as they camped in a vast Muslim graveyard on a hill near Thatta city.

Hordes of people ran after vehicles distributing food and water near the graveyard, a chaotic effort that left many flood survivors — especially the old and infirm — with nothing. Some drank rainwater pooled on the ground.

"I cannot run after food and survive the maddening rush at this age of mine," said 75-year-old Nasima Mai, who fled with her extended family, mostly women and children.

"They throw food from the truck like animals are given food," she said.

Authorities said they were trying to provide food and shelter to the hundreds of thousands of people camped out on the hill in Makli. But as in other areas of the country, the scale of the disaster has overwhelmed both local capacity and the international partners trying to help.

"We are trying to set up a tent city in different parts of Makli so that the distribution [of aid] could be organized," said Hadi Baksh, a disaster management official in southern Sindh province.

The floods started about a month ago in the northwest after extremely heavy monsoon rains and have slowly surged south along the Indus River, devastating towns and farmland. More than 1,600 people have died and 17 million more are affected by the floods.

Authorities struggled to save Thatta on Sunday, building new levees across a major road to hold back floodwaters that inundated the nearby town of Sujawal. Many of Sujawal's residents had already fled, but the water damaged houses, schools and other buildings.

Most of Thatta's 350,000 residents had also fled in recent days but began to return to the city as the danger passed, Baksh said.

"We have raised the level of the ground and constructed a levee on the bypass to stop the water, and now the chances are very low that the water might run into the city," said Baksh.

Thatta, which is about 125 kilometres southeast of the major coastal city of Karachi, contains several well-known mosques, including one built by Shah Jahan, the ruler of the Mughal Empire in India in the 1600s.

Water levels dropping in some areas

Pakistanis displaced by flooding take shelter on an embankment near the flooded Indus River, outside Thatta in southern Pakistan on Sunday. (Kevin Frayer/Associated Press)

Water levels are beginning to drop in Sindh as the floodwaters flow down the Indus River into the Arabian Sea, Baksh said.

"In the coming days, the towns and villages will be out of flood danger," he said.

But even after the floodwaters recede, Pakistan will be left with a massive relief and reconstruction effort that will cost billions of dollars and likely take years.

Muslim countries, organizations and individuals have pledged nearly $1 billion US in cash and relief supplies to help Pakistan respond to the floods, Ekmeleddin Ihsanoglu, head of the 57-member Organization of The Islamic Conference, said Sunday.

Other foreign countries such as the United States and Britain have also pledged millions of dollars, but many officials fear Pakistan will still lack the funds necessary to recover from the worst natural disaster in the nation's history.