ISLAMABAD — The wall of floodwater that's rushing through Pakistan devastated new areas Thursday, reaching the most heavily populated parts of the country, officials and aid workers said.
The raging waters, caused by torrential rain in the north of the country, have rushed down the Indus River and inundated parts of southern Punjab province, which is home to half of the country's 170 million people. Mass evacuations began farther downriver in Sindh, which contains Karachi, Pakistan's largest city.
U.S. Army helicopters flew their first relief missions in Pakistan's flood-ravaged northwest Thursday, airlifting hundreds of stranded people to safety from a devastated tourist town and distributing emergency aid.
Four U.S. Chinook helicopters landed in the resort town of Kalam in the Swat Valley, which has been cut off for more than a week, according to an Associated Press reporter there. They flew hundreds of people — many of them vacationing there — to safer areas lower down, he said. The northwest valley is a former Pakistani Taliban stronghold.
The United Nations estimated that more than 4 million people have been affected so far by the country's worst flooding in more than 80 years, which has washed away homes, roads and crops. Parts of southern Punjab were described Thursday as a giant lake. The death toll is more than 1,600, but the precise figure is unknown.
The flooding also threatens to erode support for Pakistani President Asif Ali Zardari, whom the Obama administration considers a key ally in the war on militant Islamist groups in Pakistan and neighboring Afghanistan. In some areas, militant groups have moved to fill the vacuum left by the government's stumbling efforts to assist flood victims.
There are indications that the government in Punjab, which has had more time to prepare than other regions, is handling the crisis better than the northwestern province of Khyber Pakhtunkhwa, which was overwhelmed.
Punjab, however, is also the country's agricultural hub, and more than a million acres of crops there have been destroyed, raising fears of food shortages.