Police arrested Zaibun Nisa, now 55, in 1996 outside Islamabad after a Muslim cleric registered a complaint about the desecration of a copy of the Qur'an.

She has been held in the prison section of a mental hospital in the eastern city of Lahore for 14 years without trial because no one pursued her case.

"At her arrest, her medical examination was carried out and doctors had certified that she was mentally ill but still she was languishing in jail," her lawyer, Aftab Ahmed Bajwa, who recently took up her case with the Lahore High Court, told Reuters.

Chaudhry Mohammad Sharif, the chief justice of the high court, ordered Zaibun Nisa's immediate release, a court official said.

Bajwa said cleric informed the court that he had registered his complaint with police against "unknown people" and had never accused Zaibun Nisa of blasphemy in his complaint by name.

"What kind of a country is this where a person is being held without trial for 14 years. It can't be tolerated," Bajwa quoted the judge as saying.

Zaibun Nisa will be put in a shelter for homeless people until her family is found, Bajwa said.

Human right activists have long called for the repeal of Pakistan's controversial blasphemy law, which they say discriminates against non-Muslim religious minorities and is also used to settle personal scores.

Blasphemy carries the death penalty under Pakistani law, although the sentence has never been carried out because convictions are overturned by superior courts for lack of evidence. There have been incidents, however, where the accused have been killed by a mob.

Two Christian brothers accused of writing a blasphemous letter against the Prophet Mohammad (peace be upon him) were gunned down outside a court in the eastern city of Faisalabad on Monday.

Successive governments in Pakistan have tried to reform the law, introduced by former military ruler General Mohammad Zia-ul-Haq in the 1980s as part of his Islamization campaign, but backed down after protests from hard-line Islamic groups.