Opposition leader Benazir Bhutto flew out of Pakistan on Thursday after the Supreme Court vowed not to be intimidated by any threats of martial law when it decides whether to validate the military president's recent election victory.

A homicide bomber, meanwhile, attacked an air force bus, killing eight and wounding 40, the latest in a series of attacks against President Gen. Pervez Musharraf's security forces.

Bhutto's decision to visit family in Dubai came just two weeks after she ended eight years in exile, only to be targeted by assassins. The two-time former prime minister's on-again off-again travel plans have been a source of confusion since then.

"She has gone to Dubai to see her ailing mother and children," her spokesman Farhatullah Babar said Thursday afternoon after Bhutto was seen stepping onto an Emirates plane in Karachi. Hours earlier, Bhutto said she had decided to cancel the trip, citing lingering political uncertainties. "She will come back on Nov. 8."

Pakistan has been rocked by suicide bombings in recent weeks, deepening political turmoil ahead of a Supreme Court ruling on whether Musharraf's sweeping Oct. 6 presidential victory was constitutional. There are fears he could impose a state of emergency if judges rule against him, jeopardizing the country's transition to civilian rule.

The court, which in recent months has emerged as the main check on Musharraf's dominance, said Thursday such rumors would have no impact on its decision.

"No threat will have any effect on this bench, whether it is martial law or (state of) emergency," said judge Javed Iqbal before adjourning until Friday. The judge warned the next session after that could be Nov. 12, three days before Musharraf's current term expires.

"Whatever will happen, it will be according to the constitution and rules ... No group should think that it can take the Supreme Court hostage," he said.

Musharraf, who seized power in a 1999 coup, has pledged to quit the army before starting a new presidential term, but declined on election night to say whether he would accept a negative verdict from the court.

The doubts over his political future and what course he might take if blocked from a new five-year term has added to the climate of uncertainty in Pakistan amid the escalating violence.

Bhutto's Oct. 18 homecoming was the target of the country's deadliest-ever suicide attack, claiming more than 140 lives. Earlier this week a bomber blew himself up near Musharraf's army office in Rawalpindi, a garrison city just south of the capital, killing seven.

There have been no claims of responsibility for the recent attacks, but most have been blamed on Islamic extremists, who also have engaged in deadly clashes with the military in the volatile northwest.

With his authority and political clout fading, Musharraf agreed to a corruption amnesty to help Bhutto return to Pakistan. That followed months of talks on a possible pro-Western alliance between them to counter Islamic extremism after parliamentary elections slated for January.

Musharraf, a key U.S. ally, is under pressure from Washington to crack down on pro-Taliban and al-Qaida fighters hiding in the country's border regions near Afghanistan. But stepped-up Pakistani military action since July has sparked reprisal attacks across the country.

The suicide bombing on the Pakistan Air Force bus occurred at around 7 a.m. Thursday near an air base in Sargodha, about 125 miles south of Islamabad, air force spokesman Sarfraz Ahmed said. All the dead were air force employees, said Sahid Malik, an official at the hospital treating the victims.

Elsewhere, security forces were struggling to contain militants directly challenging the state's authority and pushing for the imposition of Taliban-style strictures on society.

In the northwestern district of Swat, where recent clashes between security forces and supporters of a pro-Taliban cleric have claimed more than 100 lives, fighting has resumed after a two-day lull.

An army helicopter attacked militants Wednesday in the Sambad area of the mountainous region 80 miles northwest of Islamabad after it came under fire. Eighteen militants were killed, including Commander Tariq, an aide to the hard-line cleric, Maulana Fazlullah, said provincial home secretary Badshah Gul Wazir.

Early Thursday, militants attacked hilltop positions of security forces in the Khwaza Khela area, triggering a gunbattle, said Ali Rahman, a local police official. He added that troops backed by helicopter gunships and artillery continued targeting militant facilities, killing at least five.

The security forces suffered no casualties, he said.