Pakistan has issued a presidential ordinance granting extra detention powers to the country's anti-graft body, which is currently investigating a case involving former Prime Minister Imran Khan, media reported on Tuesday.

Khan, the country's main opposition leader who has faced a string of cases since being ousted from power last year, was arrested in the graft case in May, which led to violent protests across the country. He was later released on bail.

The legal tweaks involved granting the anti-graft body, the National Accountability Bureau (NAB), the ability to issue arrest warrants and detain suspects for 30 days if they did not cooperate with an investigation, Geo News reported.

Pakistan's information minister did not immediately respond to a Reuters request for comment.

The move came hours before Khan and his wife were set to appear before the NAB in Islamabad and at hearings in other cases. The former premier left his home in the city of Lahore for Islamabad early on Tuesday, his party said.

The government can pass laws swiftly through a presidential ordinance when parliament is not in session, but the assembly has to endorse the law within 90 days.

Parliament was in session but was prorogued on Monday through a government notification uploaded on its website. The ordinance was issued on Monday night.

Government officials allege that Khan and his wife received land worth millions of dollars as a bribe from a real estate tycoon Malik Riaz through a charitable trust. Khan and his aides, as well as the tycoon, have previously denied any wrongdoing.

Khan and his party have faced a country-wide crackdown after the violence that followed his arrest, that included the ransacking of military installations. Hundreds of supporters and dozens of leaders were detained, and many have left his party.