The top court acquitted Asia Bibi, a mother of five from Pakistan's Punjab province, earlier in the day and overturned her death sentence, Geo News reported. She was accused in 2009 of defiling the name of Prophet Muhammed during an argument with her neighbours.
Bibi maintained her innocence, but spent most of the past eight years in solitary confinement.
The landmark ruling set off violent protests by hardliners who support strong blasphemy laws. Demonstrations against the verdict were being held in Karachi, Lahore, Peshawar and Multan. Clashes with the police were also reported, the BBC said.
"The protest for the sanctity of the Prophet has started. We will die (for the sanctity). We are not going to step back," radical Islamist party Tehreek-e-Labbaik Pakistan (TLP) -- which had threatened the judges with dire consequences if Asia Bibi was acquitted -- said in a statement.
The TLP statement cited by Efe news warned that train stations and airports would be blocked.
The Red Zone in Islamabad, where the Supreme Court is located, was sealed off by the police. Paramilitary forces were deployed to keep protesters away from the court.
Chief Justice Saqib Nisar, who read out the ruling, said Asia Bibi could walk free from jail in Sheikupura, near Lahore, immediately if not wanted in connection with any other case.
"The appeal is allowed. Sentence of death set aside. Asia Bibi acquitted of charges," said Justice Nisar.
Asia Bibi's lawyer, closely flanked by a policeman, told the BBC that he was "happy" with the verdict, but also afraid for his and his client's safety.
A police spokesperson in Lahore said that around 500 protesters had gathered outside the provincial Assembly and blocked roads in the area. "They are committing vandalism," he said.
Protests with up to 300 participants, most of them supporters of the TLP, were going ahead in many other places in Lahore.
In Karachi, demonstrations were organized in at least five places, city spokesperson Abid Hussain said. Around 300 people blocked the main entrance to Islamabad, which connects it to neighbouring Rawalpindi.
Under the Pakistan penal code, the offence of blasphemy is punishable by death or life imprisonment.
Bibi's case has attracted widespread outrage and support from Christians worldwide and condemnation from conservative Islamist groups in Pakistan, who have demanded the death penalty for her.
In 2011, senior politician Salman Taseer was shot dead by his own bodyguard for voicing support for Bibi.
Also in 2011, a Christian minority minister, Shahbaz Bhatti, was shot dead at his home for defending Bibi and opposing anti-blasphemy legislation.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
