Afghan families board a bus to depart for their homeland, in Karachi, Pakistan, on Oct 31, 2023. (PHOTO / AP)

PESHAWAR, Pakistan - More than 140,000 undocumented immigrants, most of them Afghan nationals, have returned to their Taliban-ruled homeland, Pakistani officials said on Wednesday, hours before the expiry of a deadline to expel those living in the country illegally.

Pakistan has said it will begin on Thursday an effort to round up and expel any such individuals after setting the deadline in October to begin expelling all undocumented immigrants, including hundreds of thousands of Afghans.

A senior official in the northwest province of Khyber Pakhtunkhwa bordering Afghanistan said about 104,000 Afghan nationals had left through the main Torkham border crossing during the last two weeks.

"Some of them have been living in Pakistan for more than 30 years without any proof of registration," said Nasir Khan, the deputy commissioner of the area.

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An as yet undetermined number have also left by the Chaman border crossing in the southwestern province of Balochistan.

Afghan refugees in trucks wait near the United Nations High Commissioner for Refugees (UNHCR) Azakhel Voluntary Repatriation Centre in Nowshera on Oct 30, 2023. (PHOTO / AFP)

However, Pakistan's interior ministry put the number higher, saying 140,322 of those who had stayed illegally had left.

"A process to arrest the foreigners ... for deportation has started by Nov.1," it said in a statement, while adding that voluntary return would still be encouraged.

Of the more than 4 million Afghans living in Pakistan, the government estimates 1.7 million are undocumented.

Many fled Afghanistan during its decades of internal conflict since the late 1970s, while the Taliban takeover after the US withdrawal in 2021 led to another exodus.

Pakistan said Afghan nationals have been behind militant attacks, smuggling and other crimes in the South Asian nation.

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Kabul has dismissed the accusations and rights groups have protested, asking Pakistan to reconsider.