The authorities in Islamabad shut down on Friday the holding centre built to keep illegal immigrants before deportation due to security reasons, sources said.

Thousands of undocumented immigrants are still living in the country who are being asked to voluntarily leave Pakistan through special messages, sources in the interior ministry said.

They went on to add that a large number of Afghan refugees are present at the Torkham Border to cross to their country.

The sudden increase in the movement could result in deteriorating conditions at the border, due to which the interior ministry specified a different day of action for each district, they said.

The authorities in Pakistan and Afghanistan have agreed on keeping the border open till 11:00pm, and women and children have been exempted from registration at the Torkham Border.

Read: Govt extends PoR card facility for Afghan nationals: sources

Pakistan opened more border centres on Friday to speed up the return of tens of thousands of undocumented Afghan nationals, an official said, two days after a deadline for Afghans in the country illegally to leave.

The government has brushed off calls from the United Nations, rights groups and Western embassies to think again about expelling more than a million of 4 million Afghans in the country, saying they had been involved in militant attacks and crimes that undermined the security of the country.

Facilities at the main northwestern border crossing of Torkham have been increased three times to cater for the rising number of returnees, said Abdul Nasir Khan, deputy commissioner for Khyber district.