Pakistan's anti-corruption squad apprehended Khan from the Islamabad High Court on Tuesday. A court hearing will be held at the police guest house where he is being kept, according to authorities.
The detention comes a day after the country's powerful military scolded Khan for repeatedly accusing a top military commander of planning his assassination and the previous chief of the armed forces of orchestrating his downfall last year.
In response, his Pakistan Tehreek-e-Insaf (PTI) party called for a "shutdown" across the country, with witnesses and recordings showing Khan's followers clashing with police in various cities and storming military headquarters in Lahore and Rawalpindi.
The party encouraged supporters in northwestern Khyber Pakhtunkhwa province to gather early Wednesday in Swabi City to join a convoy heading to Islamabad.
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PTI Vice Chairman Shah Mahmood Qureshi said the party's senior leadership was in Islamabad to visit Khan and will petition the Supreme Court to overturn an Islamabad High Court judgment that declared Khan's arrest valid.
"We continue to call PTI family workers, supporters, and Pakistanis to the streets for peaceful protest against this unconstitutional behavior," Qureshi wrote on Twitter.
According to a police spokesman, Khan will not be brought to court, and his planned hearing will take place at the Islamabad police lines area, where he is being held under custody.
At least one person was murdered, and 12 people were injured, including six police officers, in skirmishes in the southern city of Quetta on Tuesday, according to province home minister Ziaullah Langove.
Khan, a cricketer-turned-politician, was deposed as prime minister in April 2022 following a parliamentary no-confidence vote. Despite being injured in a November attack on his vehicle as he led a protest march to Islamabad seeking snap general elections, Khan has not halted his fight against the removal.
His detention comes when Pakistan faces its greatest financial crisis in decades, with record-high inflation and anaemic growth. An IMF bailout package has been postponed for months, although foreign exchange reserves barely cover a month's purchases.
The corruption complaint is one of almost 100 filed against Khan since he was deposed after four years in power. With a national election slated for November, Khan is often disqualified from entering public office.
Political infighting is rampant in Pakistan, where no prime minister has been in office for a full term, and the military has ruled for almost half of the country's history.
