Former PM Nawaz Sharif arrives at a court in Lahore. File photo

Pakistan's former Prime Minister Nawaz Sharif, who was convicted on corruption charges, was rushed to hospital from the prison after recent blood tests raised doctors’ concerns, his physician said on Tuesday.

The former premier was taken to hospital late on Monday, said Sharif's doctor, Adnan Malik.

Doctors initially believed Sharif had contracted dengue fever, which is rampant in Pakistan, but on Tuesday the government issued a statement saying his concerningly low platelet count may have been the results of medication he was taking.

Sharif was sentenced to 12 years in prison on corruption charges and seven years on a separate money laundering charge. He is also under investigation on other corruption allegations. Sharif has appealed the two convictions, insisting on his innocence.

In related developments, Sharif's son-in-law, Mohammad Safdar, was arrested on Monday after he alleged that Sharif was being slowly poisoned - a charge that Pakistani authorities promptly denied.

The National Accountability Bureau, which oversees investigations into corruption allegations, had questioned Sharif for the past week on corruption charges in connection with a sugar mill in which he held controlling shares while serving as prime minister.

The charges also allege that other members of his family, including his daughter Maryam Nawaz, retained shares. Sharif's daughter is appealing an earlier conviction on corruption charges against her. She was sentenced to seven years for her involvement in the purchase of apartments in London but is now out on bail during the appeal process.

Prime Minister Imran Khan's government has been relentless in pursuit of corruption cases but has come under fire for focusing most of its attention on its opponents.

As well as Sharif, the government has alleged corruption by the co-leader of another political opposition party, the Pakistan People's Party, led by Benazir Bhutto. She was killed in 2007 after returning to Pakistan from self-imposed exile. Her husband Asif Ali Zardari is in custody, under investigation on corruption charges.

The couple's son and co-leader of the party, Bilawal Bhutto Zardari, told reporters on Monday that his father was not receiving medical treatment despite a court order. It wasn't immediately clear what ailment the elder Zardari suffers from.

Associated Press