The Norwegian Refugee Council said it had registered an average of 1,000 people crossing the border daily in the first two weeks of April, which was a "sharp increase" from the first three months of the year.
"Families are telling us that without registration documents they felt forced to leave."
Since 2016 hundreds of thousands of refugees have returned from Pakistan, where some had sheltered for decades, to Afghanistan amid accusations of coercion.
They face an uncertain future in war-torn Afghanistan which is already struggling to support thousands of internally displaced people fleeing fighting.
Human Rights Watch issued a scathing report in February that accused Pakistan of coercion, threats and abuse in the mass repatriation, and the United Nations of complicity.
The report said a combination of insecure legal status, the threat of deportation during winter, and police abuses -- including extortion, arbitrary detention and night raids -- had left the Afghan refugees with no choice but to leave.
It also accused the UN's refugee agency of effectively encouraging the exodus, and said the UNHCR should end the "fiction" that the returns are voluntary.
The UN has previously rejected the criticism. This month Pakistan resumed repatriating documented refugees.
Some Afghan refugees have been sheltering in Pakistan for decades, first fleeing over the border after the Soviet invasion of 1979.
UNHCR and Pakistani officials have said some 1.34 million registered refugees remain in the country.
A further half a million undocumented refugees are also estimated to be there, making Pakistan one of the world's largest refugee-hosting nations.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)