Heavy monsoon rains are still sweeping through parts of Pakistan as surging floodwaters work their way south through the country towards the sea.
Rivers in Sindh province in the centre and south of Pakistan are now bursting their banks and authorities have evacuated more than 500,000 people in the province, which is threatened by the worst floods in 80 years, the BBC reports.
The United Nations says more than four million people have been made homeless by the flooding - the worst in Pakistan's history.
At least 1600 people are now known to have been killed in the floods.
While floods in the north-west are beginning to recede, the vast body of water has been moving down the country into new parts of Punjab and menacing Sindh province.
There are floods in the monsoon season in Sindh every year, but not on the scale expected to hit in coming hours.
United Nations officials say wells have been contaminated and there is a threat of the spread of waterborne diseases. It has sent a special envoy to Pakistan to help mobilise international support.