Hundreds of thousands of Pakistanis were fleeing a southern district Friday after the bloated Indus River crushed a levee and flooded new areas, officials said. The U.N. said as many as 1 million people have been displaced in the south since midweek.

The latest evacuations came after the Taliban issued a veiled threat against foreign aid workers helping out after the floods, a development likely to complicate the massive relief effort. More than 8 million people are in need of emergency assistance across the country.

In the southern city of Thatta, around 175,000 people _ around 70 percent of the city's population _ are believed to have fled their homes overnight, said Manzoor Sheikh, a senior government official. Authorities were trying to repair the broken levee and arranging transport for people trying to leave.

U.N. spokesman Maurizio Giuliano said according to reports received by the world body, around 1 million people have been displaced in Thatta and Qambar-Shadadkot districts since Wednesday.

It is difficult to verify figures given by the authorities because many areas are hard to reach because of the floods, and people may have left their homes well before evacuation orders.

U.N. aid agencies along with a host of other relief groups have been rushing people and supplies to affected regions as the floods have inundated Pakistan over the past month.

The situation in Sindh "is getting from bad to worse," Giuliano said. "We are delivering (aid) faster and faster, but the floods seemed determined to outrun our response."

Also at risk in Sindh province are many historic tombs, graves and other sites linked to the Mughal Empire that once ruled the subcontinent.

The floods began with the onset of the monsoon and have ravaged a massive swath of Pakistan, from the mountainous north to its agricultural heartland. Almost 17.2 million people have been significantly affected and about 1.2 million homes have been destroyed or badly damaged, the U.N. has said.

The Pakistani Taliban on Thursday hinted that they might attack the foreign aid workers. The militant network has a history of attacking aid groups, including agencies under the U.N. umbrella.

Pakistani Taliban spokesman Azam Tariq claimed Thursday that the U.S. and other countries that have pledged support are not really focused on providing aid to flood victims but had other motives he did not specify.

"Behind the scenes they have certain intentions, but on the face they are talking of relief and help," Tariq told The Associated Press by telephone from an undisclosed location. "No relief is reaching the affected people, and when the victims are not receiving help, then this horde of foreigners is not acceptable to us at all."

He strongly hinted that the militants could resort to violence.

The U.S. hopes to improve its unpopular image in the country through its aid efforts.

U.N. humanitarian chief John Holmes said the U.N. remained committed to helping the flood victims.

"We will obviously take these threats seriously as we did before, and take appropriate precautions, but we will not be deterred from doing what we believe we need to do, which is help the people of Pakistan," he told a news conference at U.N. headquarters in New York.

Other aid organizations noted that Pakistan has long been a high-risk environment for foreigners, and said their security plans took such concerns into account.

Underlining the fragile security environment, a bomb at a restaurant in the northwestern town of Mansehra killed one person Friday, local police chief Mohammed Sajjad said. He said police were investigating who planted the bomb and why.

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Associated Press writers Nahal Toosi in Islamabad and Riaz Khan in Peshawar contributed to this report.