Embattled President Pervez Musharraf on Saturday evening clamped a state of emergency in Pakistan ahead of a crucial Supreme Court ruling on the legality of his re-election, plunging the country into a fresh political crisis.An eight-member Supreme Court bench immediately set aside the Emergency order which suspended the current Constitution amid reports that Chief Justice Iftikhar Muhammad Chaudhry, who has been at loggerheads with Musharraf, has been asked to go.Musharraf, who had seized power in a bloodless coup ousting Nawaz Sharif in October, 1999, took the step as he struggled to contain the militant violence and faced serious challenge to his political authority, raising doubts over parliamentary polls planned for January."The chief of army staff (Musharraf) has proclaimed a state of emergency and issued a Provisional Constitutional Order," the state-run Pakistan TV said without elaborating.Security forces were deployed around vital installations, including state-run TV and radio stations, in the capital and other parts of the country. Army troops entered the Supreme Court building while dozens of security personnel blocked the road leading to the apex court with the judges inside, witnesses said.All land and mobile telephone services were suspended and several private TV channels were taken off air.Security forces arrested Eitzaz Ahsan, Supreme Court Bar Association chief who successfully defended Chaudhry after he was suspended in March by Musharraf. Ahsan had represented the petitioners opposing Musharraf's re-election in the Supreme Court.