MINGORA: Thousands of fearful civilians, many on foot, fled a war-torn Pakistani valley on Sunday to take advantage of a pause in fighting between the military and the Taliban.

Pakistan has urged residents of the Swat Valley to leave over the past week, while its warplanes have pounded the militant-held region in what the prime minister called a "war of the country's survival." Hundreds of thousands have already fled, adding a humanitarian crisis to the nuclear-armed nation's economic, political and other woes.

As soon as a curfew was lifted early Sunday, residents in major Swat towns began to leave in any way they could. In the main Swat city of Mingora, Taliban militants were still visible, but no skirmishes were reported, and no fighter jets were seen overhead.

"We are going out only with our clothes and a few things to eat on the long journey," said Rehmat Alam, a 40-year-old medical technician walking out of Mingora with 18 other relatives. "We just got out relying on God because there is no one else to help us." Officials said the curfew would be back on by early afternoon.

The brief lull in fighting allowing residents to get out could signal that the army plans to increase its aerial and other attacks later Sunday.

Amid praise from Washington, Pakistan's leaders launched the full-scale offensive Thursday to halt the spread of Taliban control in districts within 60 miles (100 kilometers) of the capital, Islamabad.

The goal is to wrest Swat and neighboring districts from militants who also dominate the adjoining tribal belt along the Afghan frontier, where U.S. officials say al-Qaida chief Osama bin Laden may be hiding.

Many displaced civilians have arrived at relief camps throughout the northwest, while others are believed to have headed to other parts of Pakistan to stay with relatives.

The international aid agency World Vision said its relief workers were finding "intolerable" conditions at some camps due to soaring temperatures, overcrowding, inadequate toilets and a lack of electricity.

"Despite the coordinated efforts of the Pakistani authorities, World Vision and other aid agencies on the ground, we may not be able to meet the most basic needs of the refugees as quickly as they are arriving in the camps if it continues at this pace," said Jeff Hall, an official with the aid group.

Prime Minister Yousuf Raza Gilani directed millions of dollars to help the residents of a region where faith in the government is shaky, saying the army "can only be successful if there is support of the masses." Witness accounts indicate that scores of civilians have already been killed or injured in the escalating clashes in the Swat, Buner and Lower Dir districts.

Taliban militants seized much of the area under a peace deal, even after the government agreed to their main demand to impose Islamic law in the region. U.S. officials likened the deal to a surrender. Pakistani leaders said the agreement's expected collapse had opened the eyes of ordinary citizens to the extremist threat.

The army says 12,000 to 15,000 troops in Swat face 4,000 to 5,000 militants, including small numbers of foreigners and hardened fighters from the South Waziristan border region.

The military said its helicopter gunships attacked militant hide-outs in Mingora and killed 15 fighters Saturday. An estimated 30 to 40 more died in smaller clashes elsewhere, the statement said.

Four soldiers were wounded. The casualty tolls could not be independently verified.

The army accused militants of causing civilian casualties with indiscriminate mortar fire. However, officials have given no details of civilian casualties, apparently for fear of a public outcry that could make it hard for the army to press ahead.

Pakistan is also trying to eliminate militant sanctuaries in its semiautonomous tribal belt along the Afghan border.

A militant attack on a security convoy in South Waziristan tribal region Saturday prompted a clash that left 18 militants and one soldier dead, a military official said.

The official spoke Sunday on condition of anonymity because he lacked clearance to speak to media on the record.

South Waziristan is the main base for Pakistan's top Taliban leader, Baitullah Mehsud.