As Pakistan's floods continue to sweep southward, the government has warned residents of three towns to evacuate after floodwaters breached an embankment.
Hadi Bakhsh Kalhoro, a senior official in the local Thatta district government, told the AFP news agency that floods had caused a breach in one of the embankments at the village of Surjani, close to the Indus river, threatening the rest of the area.
Around 400,000 people normally live in the threatened towns of Sujawal, Mirpur Bathoro and Daro in Pakistan's southern Sindh province, but most were thought to have fled already.
Farther north along the Indus, Pakistani authorities were also struggling to block rising floodwaters from overrunning the city of Shahdadkot, home to some 100,000 people, and to rescue thousands from at least 25 nearby villages.
But elsewhere in the Sindh province, floods had washed away at least 40 other villages, and the United Nations has estimated that 800,000 people throughout Pakistan remain so isolated by the floods that they can only be reached by air.
In areas near Hyderabad, Sindh's second-largest city, the Indus has swelled from its normal width of 200-300 metres to almost three and a half kilometres, an army spokesman said.
"Really the problem in the lower Sindh district is quite different than elsewhere, because it's flat," Al Jazeera's Zeina Khodr, reporting from Hyderabad, said.
The floods that have submerged large areas of Sindh are not expected to recede for months, Khodr said, and evacuees are not getting much food or aid.
Meanwhile, an anonymous US official told the AFP that the Tehrik-e-Taliban in Pakistan is planning to attack foreign aid workers participating in flood relief.
But the US general overseeing American flood-relief efforts, Brigadier General Michael Nagata, said Wednesday that his troops had not experienced any "security threats" in their three weeks of work.
In general, Pakistani forces are distributing the aid being ferried into the country on US planes and helicopters, but they are also guiding American pilots through rugged terrain in the country's northwest and occasionally working together in public.
Maurizio Giuliano, a spokesman for the UN office for humanitarian affairs, declined to comment specifically on the US warning but acknowledged that UN workers in Pakistan had been targeted before.
"The host government is happy with us," Giuliano said, and it would be inhumane to attack or kidnap people working "day and night" to save lives.