Pakistani former Prime Minister Imran Khan was taken into custody by paramilitary forces on Tuesday.
The former leader was arrested during a court appearance in Islamabad over anti-graft charges.
"Imran Khan has been arrested in the Qadir Trust case," the Islamabad police said on Twitter.
Interior Minister Rana Sanaullah told reporters that Khan was arrested by Pakistan's anti-corruption body, the National Accountability Bureau (NAB), after he did not appear before a tribunal "despite notices."
The NAB had issued arrest warrants for Khan on May 1, accusing him of "corruption and corrupt practices."
In a pre-recorded video released by party officials, Khan said "by the time these words reach you I would have been detained under an illegitimate case."
It appears late Tuesday that Twitter, Facebook and YouTube have been restricted across Pakistan, according to internet monitoring company Netblocks.
How did Khan's party react?
Officials from Khan's Pakistan Tehreek-e-Insaf political party have urged supporters to take to the streets and "shut down Pakistan" in protest.
"Pakistan's people, this is the time to save your country. You won't get any other opportunity," the party said on Twitter.
However, police have vowed to strictly enforce an order prohibiting gatherings of more than four people.
Khan's close aide, former information minister Fawad Chaudhry, denounced the arrest as an "abduction."
Footage broadcast on national television showed Khan being manhandled by dozens of paramilitary rangers and taken into an armored car.
"As we reached court's biometric room to mark the attendance. dozens of rangers attacked us," Ali Bukhari, a lawyer for the party, told the AFP news agency. "They beat him and dragged him out."
A scuffle also broke out between Khan's supporters and police outside the court. Some of Khan's lawyers and supporters were injured, Chaudhry said.
Khan's party complained to the court, which requested a police report explaining the charges for Khan's arrest.
Protests erupt following Khan's arrest
Protests erupted across Pakistani cities, with Khan's supporters blocking roads in capital Islamabad, Peshawar and other cities.
Some stormed the residence of the corps commander in Lahore, while others laid seige to a gate of the army's headquarters in the garrison city of Rawalpindi.
Pakistan's political crisis
Khan was ousted by a no-confidence vote in April 2022. He claims his ouster was illegal and part of a Western conspiracy.
Khan has campaigned against the government of his successor Prime Minister Shahbaz Sharif, and demanded early elections.
The conflict between the two politicians has escalated amid the country's worst economic crisis in decades. Khan's supporters have clashed with police on several occasions.
In recent days, Khan has accused a senior intelligence officer, Major-General Faisal Naseer, of being involved in an assassination attempt last year during which he was shot in the leg. The military said these comments were "fabricated" and "unacceptable."
Anonymous officials from the NAB told the Associated Press that Khan will be brought before an anti-graft tribunal later on Tuesday.
Khan has almost 100 cases registered against him since he was ousted — a tactic analysts say successive governments have used to silence their opponents in a country where the military holds undue influence.
In most cases, he faces being barred from public office if convicted.
rm, zc/sms (Reuters, AP, AFP, dpa)