Pakistan's Supreme Court has upheld the acquittal of a Christian woman charged with blasphemy, standing by its earlier verdict that sparked days of protests, death threats and nationwide chaos.

The country's top court in the capital, Islamabad, on Tuesday, dismissed the review petition against Aasia Bibi, who spent eight years on death row for blasphemy before being released last October.

The three-judge panel said arguments of the lawyer acting on behalf of the petitioners did not satisfy the judges.

"On merit, this petition is dismissed," Chief Justice Asif Saeed Khosa said in court.

She is now free to leave the country. Unconfirmed Pakistani media reports said her two daughters have already gone to Canada, where they've been granted asylum.

Bibi is currently under guard at a secret location in Pakistan for her own safety.

"I am really gratefully to everybody. Now after nine years it is confirmed that I am free and I will be going to hug my daughters," a friend quoted Bibi as saying to The Associated Press, on condition of anonymity fearing for his own safety.

Her lawyer, Saiful Malook, who returned to Islamabad after fleeing the country amid death threats, called the decision a victory for Pakistan's constitution and rule of law.

'Duty to protect'

Amnesty International issued a statement calling for her to be allowed to "reunite with her family and seek safety in a country of her choice".

"The authorities must also resist and investigate any attempts to intimidate the Supreme Court. They have a duty to protect against threats of violence to harm religious minorities or the lives of judges or other government officials," said Amnesty South Asia campaigner Rimmel Mohydin.

The 54-year old was arrested in 2009 after being accused of blasphemy following a quarrel with two female Muslim farm workers who refused to drink from a water container used by a Christian in a village in eastern Punjab province.

Bibi has always denied committing blasphemy.

The case became emblematic of fair trial concerns around Pakistan's strict blasphemy laws.

The far-right Tehreek-e-Labbaik Pakistan (TLP) threatened to hold protests if Bibi's acquittal was not reversed.

Judge Khosa said in court that Bibi's accusers were guilty of perjury, and if the case hadn't been so sensitive, they should have been jailed for life.

"The image of Islam we are showing to the world gives me much grief and sorrow," said Khosa.

Call for violence

TLP called for its members to be ready for action in a message sent to journalists prior to the ruling.

But most of its leaders remain in detention after a government crackdown, and few protesters could be seen at the court in Islamabad, where security appeared as normal.

That did not prevent those who did show up for the hearing from calling for violence against Bibi. "She deserves to be murdered according to shariah," Hafiz Ehtisham Ahmed, an activist linked to the Red Mosque in Islamabad, told AFP news agency.

"If she goes abroad, don't Muslims live there? If she goes out of Pakistan ... anybody can kill her there."

Al Jazeera's Kamal Hyder, reporting from Islamabad, said: "This is indeed a landmark case. Security forces are on high alert, just in case there is a reaction across the country."

Blasphemy remains a massively inflammatory issue in Pakistan, where even unproven accusations of insulting Islam can prompt lynchings. Many cases see Muslims accusing Muslims, and rights activists say blasphemy charges are frequently used to settle personal scores.

Minorities, particularly Christians, are often caught in the crossfire.