ISLAMABAD, Pakistan — Pervez Musharraf, Pakistan's former military ruler, was suddenly taken to a military hospital on Thursday while he was being transported to a hearing to face accusations of treason, lawyers and police officials said.

A senior police official told Justice Faisal Arab, who is heading a three-member panel of the special court that is hearing the case, that Mr. Musharraf had developed a "heart problem."

Mr. Musharraf, a former army chief, had just reached the premises of the court in Islamabad, Pakistan's capital, when his convoy abruptly went to a hospital in the neighboring garrison city of Rawalpindi.

A spokesman for Mr. Musharraf said he was admitted to the intensive care unit of the Armed Forces Institute of Cardiology and was undergoing tests.

Mr. Musharraf, 70, who seized power in a military coup in 1999 and ruled until he was forced to resign in 2008, is accused of subverting the Constitution when he imposed emergency rule in November 2007.

The treason proceedings are unprecedented in the country's history. However, Mr. Musharraf has denounced the trial as a political vendetta and has challenged the legality of the special court.

He has been reluctant to appear at the hearings and his lawyers have been pressing for him to be exempted from having to attend. However, Justice Arab, the presiding judge, has remained firm in demanding that Mr. Musharraf should appear before the court.

Akram Sheikh, a government prosecutor, said that Mr. Musharraf was using illness as an excuse to avoid attending the hearing.

Two earlier hearings were canceled after explosives were discovered on the route to the court from his farmhouse on the outskirts of Islamabad.

On Dec. 26, Justice Arab had directed the authorities in Islamabad to ensure Mr. Musharraf's appearance at any cost. At least 1,600 police officials were deployed on the route Mr. Musharraf was to take from his residence to the court. All pedestrian and vehicular traffic has been stopped for Mr. Musharraf's journeys to the court.

Earlier on Thursday, prosecutors and Mr. Musharraf's lawyers traded barbs, accusing each other of threats and provocation.

Rana Ijaz, one of Mr. Musharraf's lawyers, said that Mr. Sheikh, a prosecutor generally seen as sympathetic to Prime Minister Nawaz Sharif, whom Mr. Musharraf ousted in the 1999 coup, was planning to throw a shoe at Mr. Musharraf to humiliate the former ruler.

Mr. Musharraf's lawyers denied that he was trying to avoid attending or was frightened.

"If you are aware of his temperament, he is not one to be scared," Ahmad Raza Khan Qasuri, one of his lawyers, said. "He knew these political jokers will make false cases against him. He will be honorably acquitted."

The treason accusation is the most serious challenge Mr. Musharraf has faced since his return to the country in March last year. However, his ambition of reviving his political fortunes foundered after his party, the All Pakistan Muslim League, received a tepid response from the public and Mr. Musharraf found himself ensnared in a series of court cases.