Mr Khan, 70, has been in jail since he was given a three-year sentence on August 5 on charges of unlawfully selling state gifts during his time in office from 2018 to 2022.
As a result of the conviction, he was also barred from standing for elections for five years. Pakistan is due to hold a general election later this year but the polls may be delayed due to the redrawing of constituencies based on the country's latest census.
The former prime minister has said he has faced many charges – about 200 in all – including treason and terrorism.
He was hit the series of charges after he was removed from office in a no-confidence vote in April last year. He has said that the cases are politically motivated.
Ongoing criminal charges
The cricket star-turned-politician has also been previously denied bail in at least nine other cases, including three in anti-terrorism courts and six in the district courts in Islamabad.
An official from Mr Khan's Pakistan Tehreek-e-Insaf, or PTI, party said on Tuesday that the Islamabad High Court had suspended the sentence imposed by the lower court.
In his appeal, Mr Khan said he was convicted without being given the right to prepare his defence.
A newly established specialised court designated for lawsuits involving the Official Secrets Act has instructed the authorities of Attock jail, where Mr Khan is being held, to maintain him in judicial confinement.
The court has ordered for him to be presented on August 30 in relation to the Cipher case, which involves a diplomatic record that purportedly disappeared from Mr Khan's possession.
PTI claims that the diplomatic communication proves the US was pressuring the Pakistani political opposition to rally against Mr Khan and expel him from government.
A legal letter, a duplicate of which has been seen by The National, has been sent to the superintendent of Attock jail by Islamabad High Court Judge Abul Hasnat Muhammad Zulqarnain.
It confirms that he will remain in custody and that “the accused Imran Khan Niazi, son of Ikramullah Khan Niazi R/o Zaman Park, Lahore, is hereby ordered for Judicial Remand in case FIR mentioned above, who is already detained in district jail, Attock”.
In the Pakistani and Indian justice systems, an FIR is a legal report on a criminal case.
Legal proceedings against PTI vice chairman and former foreign minister Shah Mahmood Qureshi in connection with the same case are also ongoing.
One of Mr Khan's lawyers told reporters outside Attock jail, which was surrounded by patrolling police officers, that the former prime minister was “on judicial remand” and would appear before a special court in Islamabad on Wednesday.
Rights monitors say authorities use vexing and repetitive legal proceedings as a tactic to quash dissent in Pakistan.
Pro-PTI lawyers chanted “Release Imran Khan” and “Khan, your devotees are countless” outside the court as initial news of his sentence suspension broke.
The party later said nine activists had been arrested outside the jail.