Zambia's President Hakainde Hichilema has pardoned former defence minister Geoffrey Bwalya Mwamba, popularly known as GBM, who has been serving a five-year prison sentence for corruption.

Mwamba was freed on medical grounds amid a social media storm on the state of his health in prison.

Security Minister Jack Mwiimbu told journalists on Thursday that the former minister had petitioned the president in February for his release, the public broadcaster ZNBC reports.

Mwamba has withdrawn his appeal against the conviction as part of the conditions for his release, it adds.

Worsening cancer

Last month the former minister moved to court to seek his release on medical grounds in order to receive treatment abroad for worsening prostate cancer, according to local reports.

His lawyers were quoted as saying that the required treatment was unavailable in Zambia.

Mwamba served as defence minister under President Michael Sata's administration from 2011 to 2013. He was Hakainde's running mate in the 2016 presidential election although they lost.