ISLAMABAD — Pakistan's prime minister has been 'disqualified' from office due to an earlier contempt conviction, the top court declared Tuesday, a ruling that was likely to usher in new political turmoil in the nuclear-armed country.

Yousuf Reza Gilani's party is the largest in Pakistan's ruling coalition, and has said in the past it would have the numbers to elect a new premier if Gilani were ousted. A worst case scenario would be institutional deadlock coupled with social unrest, something that could raise the possibility of the army stepping in, as it has done three times in the country's past.

In its ruling, the Supreme Court ordered the country's election commission to formally dismiss Gilani and said he hadn't legally been the prime minister since April 26, when the court convicted him for contempt for refusing to open a corruption probe against his boss, President Asif Ali Zardari.