ISLAMABAD: The kidnapped son of a former Pakistani prime minister has been rescued in Afghanistan in a joint operation by Afghan and US forces, three years after gunmen abducted him in his Pakistani home town, officials said on Tuesday.

Ali Haider Gilani, son of ex-premier Yusuf Raza Gilani, "has been recovered today in a joint operation carried out by the Afghan and US security forces in Ghazni, Afghanistan", the Pakistani foreign office said in a statement.

It added that he would be transferred to Pakistan after a medical check-up.

In a separate statement, Afghan President Ashraf Ghani's office said Afghan security forces defeated an al Qaeda cell in a joint operation with international forces, and suggested that the discovery of Gilani may have been accidental.

"During this anti-insurgency operation, Ali Haider Gilani ... was identified at the site of the operation, and was freed from terrorists," it said.

According to Ghani's office, the raid occurred in neighbouring Paktika province, which also borders Pakistan's restive tribal areas.

US forces in Afghanistan confirmed Gilani had been rescued in a joint raid with Afghan commandos in the Gayan district of Paktika, according to a statement released on Tuesday.

Four enemy combatants were killed during the operation, which involved US special forces and was carried out under the "Freedom's Sentinel" counter-terrorism mandate.

"When we first heard the news, we didn't believe it and only believed it once the foreign office confirmed it," Ali Musa Gilani, Ali Haider's brother, told Pakistan's Geo TV.

"Right now, we don't have any plans to celebrate. We are just waiting to see his face."

Ali Haider was abducted outside an office of the Pakistan Peoples Party (PPP) in his home town of Multan, in southern Punjab province, two days before Pakistan's landmark May 11, 2013 general election.

His father, a veteran PPP member, was prime minister from 2008 to 2012, when he was removed from office by the Supreme Court over contempt of court charges related to his refusal to reopen corruption cases against then-president Asif Ali Zardari.

A smiling Yusuf Raza Gilani was seen hand-in-hand with PPP chief Bilawal Bhutto Zardari at an election rally in Pakistan-administered Kashmir shortly after news of the release broke.

He briefly thanked supporters for their prayers and good wishes during his speech to the crowd.

Ali Haider's was not the only high-profile abduction in Pakistan in recent years.

The son of a Pakistani governor, assassinated for criticising the country's harsh blasphemy laws, was kidnapped in 2011. Shahbaz Taseer was recovered in the southwestern city of Quetta in March.