ISLAMABAD, (Reuters) – The United Nations launched an appeal on Friday for $543 million for more than 2 million people displaced by fighting in northwest Pakistan, where officials said villagers were turning against the Taliban.

The military launched an offensive this month in the picturesque Swat Valley and neighbouring districts to stop the spread of a Taliban insurgency that had raised fears for nuclear-armed Pakistan’s future.

Officials have warned that the militants might try to strike back. A car bomb which exploded outside a cinema in the northwestern city of Peshawar on Friday killed six people and wounded about 75, hospital officials said. There was no claim of responsibility.

The United Nations has warned of a long-term humanitarian crisis and called for massive aid for nearly 1.7 million people displaced by the offensive and about 555,000 people forced from their homes by earlier fighting in the region.

“The scale of this displacement is extraordinary in terms of size and speed and has caused incredible suffering,” said Martin Mogwanja, the acting U.N. humanitarian coordinator, in launching the “flash appeal”.

“We require a total $543 million assistance until the end of December this year,” Mogwanja told diplomats and reporters.

The appeal came a day after donors promised $224 million, including $110 million from the United States. The government has warned the militants could exploit a failure to help.

The United States, which sees Pakistan as vital to its plan to defeat al Qaeda and bring stability in Afghanistan, has applauded Pakistani resolve to fight what some U.S. leaders have called an “existential threat” to the country.

Even if the Pakistani military defeats the Taliban quickly and people can go home soon, they will need help for months because their crops are rotting in the fields, aid officials say.

Pakistan could face greater turmoil in the months ahead.

U.S. Joint Chiefs of Staff Admiral Mike Mullen said on Thursday a U.S. military offensive in southern Afghanistan could push Taliban fighters into Pakistan.

The United States is pouring thousands of extra troops into Afghanistan this year to try to reverse gains by a resurgent Taliban, particularly in its southern heartland.

About 15,000 members of the security forces are fighting between 4,000 and 5,000 militants in Swat, the military says.

Pakistan says more than 1,000 militants and more than 50 soldiers have been killed in the fighting. There has been no independent confirmation of the estimate of militant casualties.

The government has the backing of most politicians and many members of the public for the offensive but that support could quickly disappear if many civilians are killed or if the displaced languish in misery.

In a sign of growing hostility towards the Taliban, villagers in two northwestern districts were raising militias, or lashkars, to try to expel the gunmen, officials said. “They are resolutely defending against the advance of the Taliban. That is the silver lining that I can see,” Major-General Sajjad Ghani, who is leading the offensive in the upper part of Swat, told a small group of visiting journalists.

Provincial assembly member Jafar Shah said a clash had erupted on Thursday between Taliban and villagers in the Kalam region to the north of Swat and several people on both sides were wounded or killed.

Villagers had taken the same stand in parts of Lower Dir, to the west of Swat, and the Taliban had pulled out of some areas, a provincial official said.

In Swat, soldiers advancing from three directions battled militants in several places. The military said late on Friday 17 militants and three soldiers were killed in heavy exchanges of fire in the previous 24 hours.

The head of the government relief operation, Lieutenant General Nadeem Ahmed, said on Thursday up to 200,000 civilians were stranded in the valley and authorities might have to drop food to them from the air.

President Asif Ali Zardari has said that after Swat, the army would move against militants in Waziristan.