Pakistan has told 50,000 Afghans to leave the Bajur tribal region, accusing them of links to militants that used the remote and impoverished area as a base for attacks on both sides of the frontier.
Bacha Khan, a police official at the Toorwandi border post in Bajur, told The Associated Press on Tuesday that some refugees have crossed into Afghanistan and others moved to other parts of Pakistan.
U.S. officials concerned about the escalating insurgency in Afghanistan have praised the military operation in a region that has been touted as a possible hiding place for al Qaeda chief Osama bin Laden.
Pakistan's army claims to have killed more than 1,000 insurgents in two months of fighting. It has given no figure for civilian casualties, but acknowledges that many villages have been devastated by airstrikes, artillery fire and gunbattles.
Khan had no figures for how many Afghans have left since officials distributed leaflets in Bajur last week telling them to go.
However, he said an estimated 20,000 refugees had returned home in recent weeks. Thousands more went to other parts of Pakistan, he said.
An Afghan community leader in Khar, Bajur's main town, urged the government to provide transportation for the refugees. "We are poor people, and we don't have enough money to pay for the buses," Ghulam Jan told an AP reporter.
Authorities were threatening to deport those who resisted and to demolish their houses. Iqbal Khattak, a government official in Khar, said 45 Afghans had been detained by Tuesday and some Afghan-owned shops sealed.
Pakistani officials say the fighting in Bajur has displaced up to a half-million people - roughly half the region's population. Most are in nearby areas of Pakistan with relatives or in camps.
The U.N. refugee agency said last week that 20,000 people had moved into the neighboring Afghan province of Kunar. It described them as "Pakistani families" and forecast they would return after the fighting.
Kunar provincial Police Chief Abdul Jalal Jalal said Tuesday that 30,000 people had arrived from Pakistan.
Of 4,140 families there, 70 percent were Pakistani and 30 percent Afghan, said Sardar Khan, an official dealing with refugees in Kunar. He said seven families arrived Monday.
"They are very poor families," Khan said, and residents are sheltering them in their homes. Relief agencies and the government were scrambling to build one-room shelters in time for winter, he said.
Afghans flooded into Pakistan during more than 20 years conflict before U.S.-led forces toppled the Taliban government in 2001.
According to U.N. figures, more than 5 million have since returned. Pakistan complains that refugee camps and Afghan communities remain hotbeds of militant activity and has been pressing for them to be cleared.
Militants have responded to the military operations in Bajur and other regions in the northwest with suicide attacks, including the deadly Sept. 20 truck bombing at the Marriott Hotel in Islamabad.
President Asif Ali Zardari has described the hotel bombing as Pakistan's 9/11 and sought to talk his fellow citizens out of the widespread belief that the country is fighting "America's war" and paying an unacceptable price.
The government has called an emergency session of parliament Wednesday to discuss the security situation.