Pakistan's Supreme Court has acquitted a Christian woman convicted for blasphemy, prompting sporadic protests by far-right groups that have been demanding her execution for years.

Aasia Bibi was cleared of all blasphemy charges and authorities were ordered to release her after nine years on death row, Cheif Justice Saqib Nisar announced in the capital, Islamabad, on Wednesday.

"This appeal is allowed. The judgements of the High Court as well as the Trial Court are reversed. Consequently, the conviction as also the sentence of death awarded to the appellant is set aside and she is acquitted of the charge," Nisar told a packed courtroom.

Bibi, 53, a native of the central Pakistan village of Ithan Wali, was accused by two Muslim women of having insulted Islam's Prophet Muhammad and the Quran during an argument sparked by their refusal to drink water from the same vessel as her in 2009.

She was convicted and sentenced to death by a trial court in November 2010, with the Lahore High Court upholding her conviction four years later.

Rights groups and Bibi's lawyers, however, argued that there were numerous fair trial concerns in her case, one that became emblematic of such concerns in many cases under Pakistan's strict blasphemy laws.

Blasphemy against Islam and its Prophet is a sensitive subject in Pakistan, where the crime can carry a compulsory death sentence.

Increasingly, blasphemy accusations have resulted in mob lynchings and extrajudicial murders. At least 74 people have been killed in violence related to blasphemy allegations since 1990, according to an Al Jazeera tally. Those killed include a provincial governor who stood up for Bibi when she was first accused in 2009.

On Wednesday, judges said they agreed that Bibi had not been tried fairly, noting "glaring and stark" contradictions in the prosecution's evidence, and ordered her immediate release.

Justice Asif Khosa, writing in the full verdict, issued shortly after Wednesday's announcement, said the truth had not been fully revealed during the trial. (Aljazeera)

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