Pakistani Prime Minister Imran Khan faces being booted from office on the weekend after the Supreme Court ruled (on Thursday) that the parliament had been illegally dissolved and a no-confidence vote on his government must go ahead.

Khan's coalition lost its majority in the national assembly last week, but he avoided being dismissed when the deputy speaker blocked a no-confidence motion against him and the president dissolved parliament and ordered fresh elections.

"All actions taken are of no legal effect and quashed," the Supreme Court said after hearing four days of arguments on the matter.

"The national assembly continues to remain in session," it added, with officials saying it would sit again on Saturday.

The court's judgement was broader than expected after the chief justice said earlier this week they would only rule on the legality of the no-confidence motion being blocked.

Khan, a world-class cricketer before turning to politics, said he would call a cabinet meeting on Friday and address the nation in the evening.

"I have always and will continue to fight for Pak till the last ball," he tweeted.

Shehbaz Sharif, head of the Pakistan Muslim League-N (PML-N) and likely to be the next prime minister, said the court's decision "has saved Pakistan and the constitution of Pakistan".

Pakistan People's Party (PPP) leader Bilawal Zardari Bhutto, who had joined forces with Sharif to oust Khan, tweeted: "Democracy is the best revenge".

Pakistan has been wracked by political crises for much of its 75-year existence, and no prime minister has ever seen out a full term.

(With input from AFP)