ISLAMABAD: Former Pakistani prime minister Imran Khan on Tuesday was questioned by an anti-graft agency on corruption charges, his lawyer said, less than a week after he rejected a summons to appear and denounced the allegations against him.

Khan, who says corruption charges have been concocted, is embroiled in a confrontation with the powerful military, which has ruled Pakistan directly or overseen civilian governments throughout its history.

Khan was arrested and detained on May 9, sparking widespread protests by his supporters, and raising new worries about the stability of the nuclear-armed country as it struggles with its worst economic crisis in decades.

Khan was later freed on bail.

"He has joined investigation," said his lawyer, Faisal Chaudhry, referring to his questioning by officials of the National Accountability Bureau (NAB).

His wife, Bushra Khan, who also faces graft charges, had joined him but only Imran Khan had been questioned as of early Tuesday afternoon, Chaudhry said. She has not commented on the charges against her but Khan has rejected them.

The former international cricket star became prime minister in 2018 with the tacit support of the military, though both sides denied it at the time, but he later fell out with generals and was ousted as prime minister after losing a confidence vote in 2022.

Khan, 70, has since then been campaigning for a snap election, with rallies with his supporters across the country.

The prime minister who replaced him, Shahbaz Sharif, has rejected Khan's call for a general election before it is due late this year.

Khan won widespread popularity among Pakistan's 220 million people with a conservative, nationalistic agenda, and that support has been reinforced more recently by his challenge to the military establishment.

The recent protests against his arrest saw his supporters ransacking the homes of senior officers and storming army headquarters, posing an unprecedented challenge to the Muslim country's most powerful institution.

The NAB, which has investigated, put on trial or jailed all those who have served as prime minister since 2008, had on May 18 asked Khan to attend the investigation, but he had declined.

The NAB had given Khan a May 25 deadline to show up, which could have led to his arrest in case of non-compliance.

The NAB arrested Khan this month on allegations that he and his wife received land worth millions of dollars as a bribe from a real estate tycoon through a charitable trust.

Khan called the allegations "absolutely false, frivolous and concocted" in a statement to NAB last week.