Interior Minister Rana Sanaullah said Khan had been arrested by the National Accountability Bureau (NAB), the country’s top anti-corruption body.
“This arrest is in accordance with the law,” he said. “NAB is an independent body and not under government control.”
The PTI promised on Twitter to challenge the arrest, saying party leadership would gather on Wednesday morning at Pakistan’s Supreme Court.
“Tomorrow, we will approach the Supreme Court to challenge the High Court decision,” Shah Mehmood Qureshi, vice chairman of the party, said in a video posted to the site.
“PTI senior leaders will meet Imran Khan at the NAB court,” he said, also calling for demonstrations to continue in a “lawful and peaceful manner” while condemning police treatment of protesters.
The arrest comes a day after the military warned Khan against making “baseless allegations” after he again accused a senior officer of plotting to kill him.
The rebuke late Monday underscored how far Khan’s relations have deteriorated with the military, which backed his rise to power in 2018 but withdrew its support ahead of a parliamentary vote of no confidence that ousted him last year.
“The timing of the arrest is striking,” said Michael Kugelman, director of the South Asia Institute at the Wilson Center.
“The senior army leadership is uninterested in repairing the rift between itself and Khan, and so with this arrest it’s likely sending a message that the gloves are very much off.”