ISLAMABAD — Pakistan's Prime Minister Imran Khan has pledged to grant citizenship to Pakistan-born children of Afghan and Bengali refugees who have been living in the country for decades.

Khan, in his first visit to commercial hub Karachi city on Monday, said hundreds of thousands of Afghans and Bangladeshis live in the country without the benefits of its social security system.

Addressing a fundraiser for dam construction, Khan said the children's lack of documentation and education has prevented them from getting jobs, so they turn to crime. He said his government will grant them citizenship.

His comments drew criticism from the opposition Pakistan People's Party. Provincial minister Saeed Ghani said Pakistan could not afford the move.

U.N. reports say Pakistan has the largest refugee population in the world, mostly from Afghanistan.