KABUL: Thousands of Afghan families are fleeing Pakistan to escape harassment after a deadly Taliban attack on a school in Peshawar in December, the head of the International Organisation for Migration (IOM) in Afghanistan said on Saturday.

More than 22,000 undocumented Afghans flocked across the border at Torkham in January, more than twice the figure for the whole of 2014, said Richard Danzinger, the IOM's mission chief in Afghanistan.

Almost 1,500 others were deported in the same month, double the number of deportees in December.

“It all started with the attack on the school in Peshawar,” Danzinger told Reuters. “When something horrible happens, people start taking it out on foreigners.”

Taliban militants attacked a school in of Peshawar in December, killing more than 130 children and prompting Pakistan to step up operations against insurgent hideouts along the border with Afghanistan.

Cooperation between Afghan and Pakistani security forces has also improved since the attack and led to the arrest of suspects in Afghanistan, where officials believe it was planned by the Pakistani Taliban.

Afghans living in Pakistan, however, face a backlash and are reporting incidents of harassment, such as raids on their homes and police coercion, according to the IOM and other officials.

Most of the Afghan families had settled in Pakistan decades earlier, Danzinger said, and had nowhere to go once they returned.

“Their lives are in Pakistan,” he said, adding it was unclear how long they would remain in Afghanistan.

The flow of undocumented returnees has increased steadily in January, rising from around 350 in the first week to around 1,400 in the final week of the month.

“It is very difficult to predict at the moment,” Danzinger said of the upward trend. “We've not seen it slow down, let's put it that way.”

The unexpected arrival of thousands has put pressure on Afghanistan's limited resources and only the most vulnerable are being given assistance.

About 10 per cent of those arriving so far have access to assistance and the IOM had been forced to pull some of its resources away from the western border with Iran to cope, Danzinger said. The IOM says it needs another $1.6 million in funds for 2015 to cope.

FO dismisses persecution claims

Pakistan's Foreign Office on Saturday dismissed IOM's concerns that the government is engaged in harassing Afghan refugees in the country.

"Afghans are our brothers and sisters. They have lived over here for more than three decades. We would like to see them return to their country with dignity and on a voluntary basis," Foreign Office spokesperson Tasnim Aslam told Dawn.com.

"We would like to hold IOM to its responsibility to look after the refugees and expect the IOM, along with the Afghan Government, to create the conditions and the pull factor in Afghanistan for their return. We are engaged with the Afghan Government. We are closely working together," the spokesperson remarked.

The spokesperson said Pakistan is encouraged by President Ghani’s statement that he attaches the highest priority to the return of Afghan refugees and we hope that the ground is being prepared for their early return.

Aslam said that, "Apart from 1.6 million Afghan registered refugees, there is an estimated equal number of Afghans who have not registered as refugees. As they have not registered themselves as refugees, it means that they are illegal aliens in Pakistan."

When asked about alleged involvement of Afghan refugees in terrorist activities in Pakistan she said that the illegal status of the refugees makes them vulnerable to exploitation by terrorists, who may find shelter in their midst.

"Naturally we discuss these matters with the Afghan Government and we do not think that this issue is going to create any friction with the Afghan Government," she concluded.