More than 2,000 civilians have fled the Pakistani military’s offensive against the Taliban stronghold in the north-west of the country, pouring over the border into Afghanistan, officials said on Tuesday.

The army on Sunday launched an offensive in the tribal region of North Waziristan, after years of international pressure to move against militants.

“At first we were suspicious that they might be insurgents in civilian clothes that could post a threat to us,” said Sahira Sharif, an Afghan parliamentarian from the eastern province of Khost.

“But when we visited them, we were sure now that they are genuine refugees,” she said.

Her province, along the border, has seen around 2,000 refugees, officials said, and the number has been increasing.

“The government is conducting a survey and our people are helping them with food and shelter,” she said.

An insurgent attack on Karachi international airport this month that killed scores was a key factor in the decision to launch the military’s offensive, according to officials and analysts.

“Despite the international pressure, the military never took the fight to the militants before,” said Afghanistan’s deputy interior minister, General Mohammad Ayoub Salangi.

“Now that they face direct and deadly threats from them, they have launched the operations.” Afghan authorities have always said that terrorist sanctuaries along the border in Pakistan were the main reason for the continuing deadly insurgency in Afghanistan.

The jihad in Afghanistan is led by the Taliban’s Mullah Omar, as well as the Haqqani network, which is based over the border in North Waziristan.

In that region, there are several foreign jihadist groups, including the Islamic Movement of Uzbekistan, involved in some of the deadliest attacks on both sides of the border.

The military says the operation, which has killed nearly 200 militants since Sunday, is not affecting any civilian areas, but the locals are still fleeing in droves.

“More than 600 families or 2,000 people, mostly from North Waziristan, have come to Gurbuz and Tani districts due to military operations launched there,” said Abdul Wahed Pathan, deputy governor of Afghanistan’s Khost province.

“We have requested the government and NGOs to assist us to provide first aid like shelter and food for them,” Mr. Pathan said.

Mokhles Afghan, an official from the neighbouring Paktika province, said that some of the refugees had gone to Khost through Paktika.

“We do not have any refugees living here but they are still coming from the North Waziristan,” he said.

“The refugees decided not to stay in our province because of the harsh summer.” “Afghanistan takes this as a humanitarian responsibility,” said Shekib Mostaghni, spokesman for the Afghan Foreign Ministry. “We will try to find aid for them.” The largely porous border is no stranger to the flow of refugees, but usually travelling in the opposite direction. For more than three decades, Pakistan has been home to millions of Afghan refugees fleeing conflict at home.

The invasion of Afghanistan by Soviet Union in 1979, the civil war between 1992 and 1996, and the Taliban regime from 1996 to 2001, sent waves of Afghan refugees into Pakistan and Iran.

Since the 2001 US-led invasion of Afghanistan, some 3.8 million people have returned home. But there are still around 2.9 million Afghan refugees in Pakistan and some 1.9 million in Iran, the UN High Commissioner for Refugees reported in 2012.

Some Afghans fear the Taliban will also flee over the border to escape Pakistan’s military. But the officials said measures are in place to stop them crossing over.

“The refugees who have stayed in Khost won’t be a threat to Afghans. Our security forces are active in the area, not only in Khost but across the country,” said General Ahmad Jan, the spokesman for 203 Military Corps, based in neighbouring Gardez city.

“Security-wise we have taken all measures so that the insurgents could not enter our soil,” deputy interior minister Salangi said.

“We believe that our intelligence agency will work seriously in this regard.” Ahmad Jan alleged the Taliban fighters have always trained on the other side of border to launch insurgency attacks in Afghanistan.

“But I believe the refugees are not the ones who will commit an attack,” he said.