The kidnapped son of Pakistan's former prime minister has been freed three years after gunmen abducted him, his party's chairman said on Tuesday.

Ali Haider Gilani, son of ex-premier Yusuf Raza Gilani, "has been recovered in a successful operation. Alhamdulillah (thanks be to God)", Pakistan People's Party chairman Bilawal Bhutto tweeted on his official account.

Pakistan's foreign office later released a statement confirming Ali Haider Gilani's release.