Islamabad - Pakistan's new government said on Monday it would put former military ruler Pervez Musharraf on trial for treason, charges punishable by death or life imprisonment.
The retired general, who returned from four years of self-imposed exile in March, has been under house arrest at his villa on the edge of Islamabad since 19 April.
Any trial could put the civilian government at loggerheads with the powerful army, which vehemently opposes the prospect of its former chief facing the courts in Pakistan.
It also threatens to sabotage the chances of a quiet deal that Musharraf's legal team had hoped would allow the 69-year-old to win bail and quietly leave the country.
Once the most powerful man in the country, Musharraf faces a slew of charges relating to his 1999-2008 rule after seizing office from then Prime Minister Nawaz Sharif, who won landmark elections in May.
"Musharraf's actions came under the purview of high treason," Sharif told parliament.
"He should face trial... and will have to answer for his guilt before the court," he added.
Attorney General Munir Malik delivered the same statement on behalf of the government in the Supreme Court. A treason trial can be initiated only by the state.
"Those who aided or abetted holding the constitution in abeyance will also be brought to justice," Malik said.
Pakistan's highest court has for months been hearing a petition from lawyers demanding that Musharraf be tried for subverting the constitution by imposing emergency rule and sacking judges in 2007.
Judge Jawad Khwaja ordered the attorney general to inform the court on Thursday about the precise steps required to bring those guilty of treason to justice.
Musharraf's office accused the Sharif government of "demonstrating recklessness" in pursuing "unwarranted" treason charges, which it warned could destabilise the country.
"The former president has served Pakistan with selfless devotion and perseverance. The people of Pakistan will not tolerate this circus, which is primarily meant to create a diversion," it said.
On Saturday, Islamist gunmen dressed as police killed 10 foreign tourists and a Pakistani at a remote base camp in the Himalayas, an unprecedented attack on mountaineers and the worst attack on foreigners in around a decade.
Musharraf's defence lawyer told reporters that putting Musharraf on trial would open "Pandora's box" in the country, which sits on the frontline of al-Qaeda and Taliban violence.
"Those who were collaborators are equally responsible, they should also be put on trial," Ahmed Raza Kasuri told reporters outside the Supreme Court.
"Whatever he did was in the interest of the state. I am confident, God willing, he will be exonerated," he said.
Pakistan's 11 May elections marked the first time that a democratically elected civilian government has served out a full five years in office and handed over at the ballot box.
It was an astonishing comeback for Sharif, who was deeply unpopular as prime minister in 1999 and whose replacement by Musharraf was widely welcomed.
In April, a caretaker government guiding Pakistan through the elections refused to initiate the trial against Musharraf, saying it was beyond its mandate and up to the new government.
Sharif did not mince his words.
"Musharraf violated the constitution twice. He overthrew an elected government in 1999 and put everything into jeopardy. He sacked judges and imprisoned them," said Sharif.
"We will follow the process of law and all political forces will be taken into confidence," he added.
The two main opposition parties, Bhutto's Pakistan People's Party (PPP) and Pakistan Tehreek-e-Insaf (PTI) led by politician Imran Khan welcomed Sharif's remarks.
"This house should have another resolution against all dictators so that no one can cast an evil eye on this house," said Syed Khurshid Shah, PPP opposition leader in the national assembly.
PTI's Shah Mehmood Qureshi said his party would support the prime minister on "every move towards supremacy of the constitution and law".
Musharraf faces three other cases dating back to his rule.
He has won bail for sacking judges and over the 2007 murder of former prime minister Benazir Bhutto, but remains under house arrest over the 2006 killing of a Baluch rebel leader.
On Monday, courts in south-western province Baluchistan adjourned until 10 July a petition seeking to move the Baluch trial to Islamabad for security reasons and the hearing on the killing to 15 July, lawyers said.
Musharraf is serving his house arrest at his luxury villa in the upmarket suburb of Chak Shahzad on the edge of Islamabad. He is currently barred from leaving the country.