Politicians, top military leaders, and diplomats were guests at the swearing-in ceremony, which took place at the presidential palace in Islamabad.

Mr. Musharraf repeated the oath administered by Abdul Hameed Dogar, the Supreme Court chief justice he hand-picked after imposing emergency rule November 3.

"I, Pervez Musharraf, do solemnly swear that I am a Muslim, that I will bear true faith and allegiance to Pakistan," he affirmed.

Mr. Musharraf won re-election in October, but political opponents rejected his victory, saying the constitution does not permit a serving army officer to hold public office.

On Wednesday, he kept his promise to resign from the military before being sworn in. But there was new violence in the city of Lahore Wednesday as police clashed with lawyers protesting Mr. Musharraf's rule.

Lawyers have been in the forefront of protests against the emergency decree, spurred by Mr. Musharraf's suspension of the constitution and his removal of Supreme Court judges he felt were hostile to his re-election. Chief Justice Iftikhar Mohammed Chaudhry was among those removed.

In a speech after taking the oath of office, the president defended his actions.

"It is most unfortunate that some elements of the judiciary, the ex-chief justice, were trying to derail the democratic transition, with all my noble intentions of following the constitution [and] removing my uniform," he said.

Opposition political parties, including those headed by former Prime Ministers Benazir Bhutto and Nawaz Sharif, are still challenging Mr. Musharraf's re-election. Almost all have registered for parliamentary elections scheduled for January, but they are holding out the threat of boycotting the vote.

The president said that would not prevent the elections from taking place.

"Elections will be held on 8th January, come whatever may. There is no going back, there is no change. So anyone who is talking of any boycotts should hear this out," said President Musharraf. 

He said the return of Ms. Bhutto and Mr. Sharif after years in exile was good for Pakistan.

"Benazir Bhutto and Nawaz Sharif are back. I personally feel this is good for the political reconciliation that I have spoken of," he said. "And I, with my inner conviction, believe that this is good for the process of political reconciliation."

The president reiterated that his country's fight against terrorism and extremism will continue, saying failure is not the option.