(CNSNews.com) - Supporters of former Pakistan Prime Minister Nawaz Sharif filed a legal appeal after his attempted return from exile - authorized by the Supreme Court - was thwarted Monday when he was deported within hours of arrival.

Despite the court ruling, the government led by President Pervez Musharraf, who toppled Sharif in a coup eight years ago, put Sharif onto a flight to Saudi Arabia shortly after he landed in Islamabad on a flight from London.

Several hundred supporters were reportedly detained at or near the airport. His Pakistan Muslim League-Nawaz (PML-N) party said it had filed a Supreme Court challenge to the government's action, arguing that it constituted contempt of court.

The deportation brought to an abrupt halt any hopes Sharif may have had of a triumphal return enabling him to rally opposition to the Musharraf government in upcoming elections. He had said before leaving London that he was returning "to give a final push to a crumbling dictatorship."

Musharraf, viewed by the U.S. government as an important ally in the struggle against Islamist terrorists, has been facing growing internal turmoil this year, under attack from Islamic radicals, the legal fraternity and opposition political parties.

Sharif has been in exile since 2000, when Musharraf freed him from a life jail term for treason and tax evasion on condition that he remain in Saudi Arabia for 10 years. Pakistan's Supreme Court ruled last month that he could return, but the government says the exile deal bars him from doing so for another three years.

Before Monday's dramatic events, Information Minister Muhammad Ali Durrani said that because of his criminal convictions, Sharif would be disqualified from contesting elections.

Musharraf's own position is looking uncertain too. The Supreme Court, headed by Chief Justice Iftikhar Chaudhary - earlier suspended by Musharraf but reinstated by court order - is reviewing petitions challenging his right to hold the country's top political and military posts simultaneously.

The court has stopped short of ordering that Musharraf may not contest the election, observing that "no-one wants to derail" the system. The case will be heard again on Sept. 15.

Musharraf's position has been looking increasingly shaky since he dismissed Chaudhary early this year, a move that triggered massive public demonstrations, leading to his eventual reinstatement.

Adding to the sense of crisis, a close ally of Musharraf's has hinted that the president could impose a state of emergency "to save his skin" - although strong indications of an imminent emergency several weeks ago turned out to be inaccurate.

He faces opposition both from rivals like Sharif and another exiled former prime minister, Benazir Bhutto, and is also under fire from militant and fundamentalist forces that regard him as a traitor for cooperation with the U.S. in the fight against terrorism.

Recently, Musharraf tried to broker a deal with Bhutto, offering to step down as chief of the army in exchange for Bhutto's support for him to serve another term as president. The proposal reportedly broke down over Musharraf's reluctance to lift a constitutional bar on prime ministers serving a third term.

Banished like Sharif on charges of corruption, graft and ill gotten wealth, Bhutto seeks immunity from prosecution and also wants future presidents to be stripped of their power to dissolve central and state governments.

(CNSNews International Editor Patrick Goodenough contributed to this report.)

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