Pakistan opened more border centers on Friday to speed up the return of tens of thousands of undocumented Afghans, the country’s official said, two days after a deadline to leave or face expulsion expired and ignoring pleas to give the plan a rethink.

Pakistan 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 Islamist militant attacks and crimes that undermined the security of the country, Reuters reported.

Afghanistan denies the accusations, saying Pakistani security is a domestic problem and calling on Pakistan to reconsider.

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.

Those arriving in Afghanistan complained of hardships they had to face to move out of Pakistan and uncertainty over their future, read the report.

"We spent three days on border in Pakistan. We had very bad situation," said Mohammad Ismael Rafi, 55, who said he lived for 22 years in the southwestern Pakistani border town of Chaman where he had a retail business.

"Thank God that we have arrived back to our country," he said. It took him six days to leave his home in Pakistan with his 16 family members and belongings to reach a makeshift tent village on the other side of the border.

Rafi accused Pakistani officials of taking bribes to process his repatriation. Authorities deny that.

He has rented a house in Kandahar before moving to his ancestral home in Helmand province.

Afghan schoolboy Sarfraz, 16, who goes by one name, said he and his father had never visited Afghanistan and did not want to go there now. His grandfather migrated to Pakistan decades ago.

The Islamic Emirate of Afghanistan (IEA), scrambling to cope with the sudden influx, has set up temporary transit camps where food and medical assistance will be provided.

In a joint statement, the Norwegian Refugee Council, Danish Refugee Council and International Rescue Committee have reported chaotic and desperate scenes among those arriving in Afghanistan.

Pakistani authorities started rounding up foreigners, most of them Afghans, hours before the deadline. Undocumented people who do not leave face arrest and forcible expulsion.

Abdul Nasir Khan, deputy commissioner for Khyber district, said 19,744 Afghans had crossed the Torkham border on Thursday, 147,949 in total since the government announced the deadline. More than 35,000 undocumented Afghans have left through another southwestern Pakistani border crossing at Chaman.

Pakistani authorities said they were open to delaying repatriation for people with health or other issues that would bar them from travelling, including a seven-month pregnant woman who was told to stay in Pakistan to have her baby and then make the journey.