ISLAMABAD, Pakistan — Afghan refugees were flowing over the border from a Pakistani battle zone Tuesday after officials accused them of links with Taliban militants and ordered them out, police said.

Pakistani authorities have told Afghans living in the Bajur tribal region to go back to their homeland and leave an area where troops have been fighting a bloody war with insurgents.

The order risked adding to the humanitarian crisis resulting from the two-month-old military offensive in a long-neglected region that had become a base for militants fighting on both sides of the frontier.

U.S. officials concerned about the escalating insurgency in Afghanistan have praised the operation, which the Pakistani military claims has killed more than 1,000 insurgents. It has given no figure for civilian casualties.

Bacha Khan, a police official at the Toorwandi border post in Bajur, told The Associated Press on Tuesday that refugees had been crossing steadily into Afghanistan, while others had moved to other parts of Pakistan.

He had no figures for how many Afghans had 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 had moved to other parts of Pakistan, he said.

An Afghan community leader in Khar, Bajur's main town, urged the government to provide transport to the refugees who complied with the order.

"We are poor people, and we don't have enough money to pay for the buses," Ghulam Jan said.

Authorities threatened to deport those who resist. Iqbal Khattak, a government official in Khar said 45 Afghans had been detained so far and some Afghan-owned shops sealed.

Pakistani officials say the fighting in Bajur has displaced up to half a million people — roughly half the population of the region. Most have found refuge in nearby areas of Pakistan with relatives or in rough 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 when the fighting stops.

Kunar provincial police chief Abdul Jalal Jalal said Tuesday that a total of 30,000 people had arrived from Pakistan.

Sardar Khan, an official dealing with refugees in Kunar, said that of 4,140 families there, 70 percent were Pakistani and 30 percent Afghan.

He said seven families had arrived Monday.

"They are very poor families. The people are giving them shelter" in their homes, he said.

Afghans flooded into Pakistan during years of conflict before U.S.-led forces toppled the Taliban government in 2001.

According to U.N. figures, over 5 million have since returned. However, Pakistan complains that refugee camps and Afghan communities remain hotbeds of militant activity and has been pressing hard for them to be cleared.

The U.N. said Tuesday that about 250,000 refugees had returned to Afghanistan so far this year and that some had cited insecurity in northwestern Pakistan as the reason they moved.

Militants have responded to military operations in Bajur and other regions with a spate of suicide attacks, including the Sept. 20 truck bombing of the Marriott Hotel in Islamabad.

The latest blast occurred Monday, when a bomber injured an opposition lawmaker and killed 17 people in Bhakkar, a town beside the Indus River.

Baitullah Mehsud, a prominent Taliban commander, issued a statement denying involvement. Some reports speculated that the motive for the attack on the lawmaker — a Shia Muslim — was sectarian.

President Asif Ali Zardari and Prime Minister Yousuf Raza Gilani both decried the blast. According to state media, Zardari said "such heinous incidents cannot deter the government's resolve to fight against terrorism."

In a bid to build political support, the government has convened a joint session of the upper and lower houses of parliament on Wednesday to discuss the security situation.

Pakistan's main Islamist party, meanwhile, stepped up its agitation against the military operations in the border region as well as Islamabad's close ties with Washington.

"Why do we get American aid? For development? No, we get it to bomb our own people," party leader Qazi Hussain Ahmed said Tuesday.