ISLAMABAD, Dec. 21 -- Pakistan's former President, Pervez Musharraf, has challenged powers of a special court constituted to try him for high treason for abrogating the country 's constitution, his lawyers said Saturday.

Prime Minister Nawas Sharif last month approved the selection of three judges for the special court, which has summoned Pervez Musharraf to appear on Dec. 24.

The government has initiated the high treason case against the former military president for suspension of the constitution when he had imposed emergency rule in November, 2007. Legal experts said the charges carry death penalty or life imprisonment.

Musharraf's lawyer, Khalid Ranjha Saturday filed a petition in the Islamabad High Court, which prayed the court to stop the special court from initiating trial of the former president.

The petition says that the former President had imposed emergency rule as the Army Chief and that he should be charged under army's law and tried in a military court.

It said Musharraf was not alone to be put on trial for imposing the emergency rule but he had consulted all stakeholders.

The petition said that treason trial only of Musharraf is against the specific constitutional provisions which guarantee fair and independent trial.

The special court, senior officials of the ministries of defence and interior have been made party in the case.

The petition was filed a day after a panel of Musharraf's lawyers in London appealed to the United Nations to intervene and stop trial of the former Pakistan President in high treason charges. They also sought help from the United States, the UK and Saudi Arabia.

The lawyers said they have sent copies of appeals to the UN Human Rights Commissioner and the UN's special adviser, responsible for reviewing the death penalty cases and checking independence of the judges.

Musharraf told two private Pakistani television channels on Thursday that he will apologize for some of his actions if that had harmed the people. He however said he had taken all decisions in the interest of the country.

It is the first time in Pakistan's 66-year history that a former military leader will be tried for high treason.

Musharraf had taken over in a bloodless coup when he had dismissed the then government of Prime Minister Nawaz Sharif in 1999.

The 69-year-old former army chief, currently lives in his farmhouse in Islamabad after he got bailed out of three high profile cases, including the 2007 assassination of former Prime Minister Benazir Bhutto.

Musharraf, who had resigned in 2008 and gone into exile, returned to the country in March this year to take part in parliamentary elections. However, a court disqualified him from standing in the May elections.