The United Nations says fresh floods in southern Pakistan have displaced about 1 million people since Wednesday.
U.N. officials said Friday the newly displaced flood victims were forced to leave their homes in Sindh province as the Indus River burst its banks.
Pakistani authorities ordered thousands of people to leave the historic town of Thatta after the Indus breached a nearby levee, but many residents have refused to leave.
The floods began almost one month ago and devastated a large portion of the country, starting in the mountainous northwest and shifting south to the agricultural heartland. The disaster has killed an estimated 1,600 people and affected up to 20 million.
Watch Ravi Khanna's Companion TV Report: U.S. Rushes More Helicopters to Help Pakistani Flood Victims
Pakistan's National Disaster Management Authority warned Friday that the death toll from the floods will rise as floodwaters recede and the missing are counted.
Watch Raw Footage of Pakistan's Flooding Conditions:
Senior Pakistani officials say the cases of waterborne diseases, such as diarrhea, are on the increase and have targeted the most vulnerable - women, children and the elderly.
NATO said Friday it was dispatching two more aircraft to Pakistan with more than 100 tons of relief goods - including power generators, water tanks and baby food. The aircraft were scheduled to leave Germany and arrive in Pakistan in the next two days.
The U.S. State Department said Thursday there is "credible" information that Pakistani militants may target foreign relief workers and Pakistani officials involved in flood relief efforts. U.S. officials said they are taking the threats seriously and working with Pakistan to boost security.
U.N. Undersecretary General for Humanitarian Affairs John Holmes said relief workers faced similar threats before the floods and will not be deterred.
Charities linked to Pakistan-based militant groups also have been providing assistance to flood victims.
Some information for this report was provided by AP and Reuters.