Pakistan's former prime minister Imran Khan has been granted two weeks of bail by Islamabad High Court in a graft case, his lawyer said.

"The court has given a two-week bail," Khan's lawyer, Faisal Chaudhry, told reporters on Friday.

The court approved the bail after the Supreme Court on Thursday said his arrest earlier in the week, which sparked riots across the country, was unlawful.

Khan arrived amid tight security at the court in Islamabad on Friday as his supporters clashed with police elsewhere in the capital, broadcaster Geo TV reported.

'Free citizen'

For a nation accustomed to military takeovers, political crises and violence, the turmoil of the past week has been unprecedented.

Since Khan's dramatic arrest on Tuesday, protesters have been clashing with police in areas around the country, and mobs have attacked military and government sites, trying to storm the military's main headquarters and burning down the residence of a top general in Lahore.

The Supreme Court ruled Khan's arrest two days ago was illegal and, while it freed him from custody, it ordered him kept under the protection of security forces in a safe location in the capital, Islamabad.

The head of his legal team, Babar Awan, underlined that Khan is a "free citizen" and will be allowed to meet with lawyers and supporters.

Chief Justice Umar Ata Bandial urged Khan to appeal to his supporters to remain peaceful.

Nearly 2,000 people have been arrested for violence since Khan's detention on Tuesday and at least eight have been killed.