Rains continue to fall in parts of Pakistan, and another surge of water is expected to reach the the province by Saturday night.
Pakistan's meteorological office expects rains to continue in the north until Sunday, and monsoon season does not end for several more weeks.
More than 1,600 people have been confirmed dead since flooding began in Pakistan more than two weeks ago, and authorities fear the death toll could be far higher. Millions have fled their homes, many of them crowding into hastily-erected camps.
The World Bank said on Friday that the flooding has also wiped out more than $1bn worth of crops in Pakistan, where food prices have already begun to rise.
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. At least 15 million people have been affected by the floods and the UN estimates up to one-quarter of Pakistan has been affected.
The UN has requested $460m from international donors, about $160m of which has been committed so far.
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," said Christopher Lom from the International Organisation for Migration. "Gradually we are hoping that the international community will become increasingly engaged and provide enough funding."
Zardari's first trip
Asif Ali Zardari, the Pakistani president, made his first visit to the affected areas on Thursday.
Zardari visited the flood zone on Thursday,
15 days after the disaster began [AFP]
Zardari's spokesman said he was briefed on the damage and the relief efforts after arriving at the Sukkur barrage in Sindh. He also met victims at a camp for displaced persons.
Security was tight, with only state media allowed access to his visit. Television showed him comforting a sobbing elderly woman, and listening to complaints from villagers.
A local official told the AFP news agency that Zardari had distributed relief goods among flood victims at the camp.
Zardari travelled to Europe at the height of the disaster, spending a week in France and the United Kingdom, a trip that earned him widespread scorn in Pakistan.