Pakistan's collision course - Musharraf's deportation of a foe raises the risk of martial law, analysts say.

After spending less than four hours on the ground at Islamabad's international airport, former Prime Minister Nawaz Sharif was bundled aboard a plane for Saudi Arabia, where he had been sent into exile seven years ago after Musharraf, an army general, overthrew him in a coup.

Monday's developments were the most dramatic so far in a months-long confrontation between pro-democracy activists and Musharraf. The general is considered a vital U.S. ally in the fight against the Taliban and Al Qaeda, despite misgivings on Washington's part about the depth of his commitment to combating Islamic militancy.

Opposition parties and lawyers groups reacted swiftly, calling for a general strike today, which could degenerate into street clashes. Sharif's party also said it would petition the Supreme Court to hold Musharraf in contempt of the panel's order authorizing the former leader's return.

Pakistanis were spellbound by the drama. In shops and restaurants, patrons clustered around televisions and radios, listening to nonstop coverage of the morning's tense events. A police blockade of the main thoroughfare leading to Islamabad's airport left thousands of commuters and travelers stranded by the roadside.

"They think this will make them look strong," said student Munir Abbas, pointing with his chin toward a knot of policemen turning cars away from the approach to the airport in the early-morning light. "But to me, it looks as if they are afraid of something."

The deportation puts Musharraf on a collision course with Chief Justice Iftikhar Mohammed Chaudhry, whom Musharraf tried to dismiss this year on misconduct charges. Suspicion that the Pakistani leader was attempting to purge the court of obstacles to another presidential term set off months of massive street protests and widespread calls for the general to step aside.

Now the chief justice is in position to preside over hearings on the deportation and on other cases that could affect whether Musharraf can persuade outgoing legislators to grant him another presidential term while he keeps his post as army chief of staff. Pakistan does not have direct presidential elections.