Rains continue to fall in parts of Pakistan, and another surge of water is expected to reach Sindh province by Saturday night.
The southern province is bracing for a second round of heavy flooding as authorities said waters have unexpectedly begun to rise at the Kotri barrage along the Indus river, and now threaten to overrun the embankments around the barrage.
Flooding at Kotri could potentially threaten the city of Hyderabad.
Residents of the city of Jacobabad in Sindh were taking no chances after warnings that a major surge was heading there from a breach in an embankment along the Indus River..
"Out of a population of 300,000, about 225,000 people have left for nearby cities and towns in the past few days," Kazim Jatoi, a city administrator, told the Reuters news agency.
Mansoor Sohail, the information ministry secretary, said on Friday that another wave of flooding could hit the country in the coming days.
The floods have also sparked health concerns, and officials have warned that fever and diarrhoea are spreading among flood victims.
In the Multan area of Punjab province, where large areas have been under water for days, medical workers have seen at least 1,000 children with illnesses such as gastroenteritis in the last three days, Mumtaz Hussain, a doctor at the main government hospital, said.
"Before the floodwater, normally we checked only 40 children a day. Now the number has increased twice," he said.
One case of cholera has also been confirmed, an official at a hospital in Mingora in Swat Valley told the Reuters news agency.
A German humanitarian organisation said there were also six suspected cases.
Dr Fozia Aziz, a health co-ordinator with the non-governmental organisation Helping Hand for Relief and Development in Islamabad, told Al Jazeera there is an urgent need to provide safe drinking water and hygienic conditions to stem the spread of diseases.
"We are conducting a number of medical camps all over Pakistan. Acute diarrhoea cases are among the most common ailments and our health workers are providing proper treatment.
"We are also giving advice to the local communities on measures to be taken to prevent or minimise the spread of disease," Fozia said, adding that several suspected cases of cholera and malaria have been reported.
Andro Shilakadze, the head of the Unicef office in Sindh province, called the situation a "heartbreaking scene".
"You see people sitting on the streets... building primitive shelters and asking for food and drinking water," he told Al Jazeera.
Flooding is expected to hit lower Sindh in the coming days [Pakistan Met Department]
"The government had established around 600 tents [for displaced people] but because of the unprecedented devastation of this flood, the need is unmatched."
The government, the United Nations and private charities have all struggled to provide relief.
The UN has requested $460m from international donors, about $160m of which has been committed so far.
"We need fast funding otherwise more people are going to die," Maurizio Giuliano, a spokesman for the UN Office for Humanitarian Affairs, said.
Aid agencies say the most urgent needs are shelter - tents, plastic sheeting and household goods - along with food and clean water. Only a fraction of the affected population has received assistance.
"That is really just a small section of the problem," Christopher Lom, from the International Organisation for Migration, said.
"Gradually we are hoping that the international community will become increasingly engaged and provide enough funding."