Pakistan's former prime minister Imran Khan was arrested by paramilitary Rangers on Tuesday while he was present at the Islamabad High Court for the hearing of a corruption case, a day after he took on the country's powerful army for allegedly hatching a plot to kill him.

His party confirmed the arrest of the 70-year-old former cricketer-turned-politician.

The arrest comes a day after the powerful army had accused Khan of levelling baseless allegations against a senior officer of the spy agency ISI.

The chairman of the Pakistan Tehreek-e-Insaf (PTI), who travelled from Lahore to the federal capital Islamabad, was undergoing a biometric process at the court when the Rangers broke open the glass window and arrested him after beating lawyers and Khan's security staff, according to senior party leader Shireen Mazari.

TV footage showed the Rangers grabbing Khan from the collar and bundling him into a prison van.

"Mr Khan has been arrested in a land transfer case to property tycoon Malik Riaz and is being handed over to National Accountability Bureau (NAB)", a NAB official confirmed to PTI.

He said that Khan has been arrested in the Al-Qadir Trust case. "His arrest warrants were issued today morning and subsequently he is arrested," he said.

"What laws? Courts attacked by Rangers as if invading an occupied land - lawyers & IHC staff also beaten. This is Pakistan today - a fascist State where the High Court has been attacked by paramilitary forces," Mazari said.

"State terrorism - breaking into IHC premises to abduct Imran Khan from court premises. Law of the jungle in operation. Rangers beat the lawyers, used violence on Imran Khan and abducted him," tweeted Mazari.

The party alleged that Khan was being tortured but it was not confirmed independently.

The Dawn newspaper reported that IHC Chief Justice Aamer Farooq directed the Islamabad police chief, the interior ministry secretary and the additional attorney general to appear before the court within 15 minutes.

Chief Justice Farooq said that he was showing "restraint" and warned that he would “summon” the prime minister if the Islamabad police chief did not appear before the court.

"Come to court and tell us why Imran has been arrested and in which case,” Justice Farooq was quoted as saying by the paper.

Islamabad police released a brief statement quoting Inspector General (IG) Akbar Nasir Khan as saying that Khan had been arrested in relation to the case which concerns allegations that Bahria Town allotted land worth Rs 530 million to Al-Qadir Trust, owned by the PTI chairman and his wife Bushra Bibi.

The police chief also said that the situation in Islamabad was "normal". He added that Section 144 had been imposed in the federal capital and action would be taken against violators.

Quoting Barrister Gohar Khan, who was at the court during Khan's arrest, Dawn said the former prime minister was "tortured".

"They hit Imran's head and leg...his wheelchair was also tossed aside during the arrest," Gohar was quoted as saying by the paper.

Former information minister and PTI Vice President Fawad Chaudhry said Khan has been abducted from Court premises and scores of lawyers and general people have been tortured. "Imran Khan has been whisked away by unknown people to an unknown location, CJ Islamabad HIgh Court has ordered Secy interior and IG police to appear within 15 min in the court," he tweeted.

Another senior leader Hammad Azhar said that Khan's arrest was "not acceptable” and asserted that the party chief "is our red line”. He called on the nation to take to the streets against Khan's arrest.

Another PTI leader Azhar Mashwani alleged that Khan had been “abducted” from inside the court by the Rangers. He said that the party had given an immediate call for staging protests in the country.

"They are torturing Imran Khan right now […] they are beating Khan sahib. They have done something with Khan sahib," another leader Musarrat Cheema said in a video message posted on the party's Twitter handle.

Khan has been facing a slew of cases since his ouster through a no trust vote in April last year. He has rejected all these cases as political victimisation by the ruling alliance.

Currently, Khan is facing over 140 cases related to terrorism, blasphemy, murder, violence, inciting to violence.