ISLAMABAD: Asia Bibi , a Christian woman on death row for blasphemy, has been put in isolation over fears of attacks by vigilantes enraged over a high-profile ruling in another blasphemy case that moderates said struck a blow against religious extremism.

Prison officials and rights activists said this week that they were concerned for Asia Bibi 's life due to the security threat and her worsening health. The move comes after "genuine" threats to her life were issued in the wake of a Supreme Court ruling that upheld the death sentence for Mumtaz Qadri , the killer of former Punjab governor Salman Taseer, who sought blasphemy law reform in a separate, high-profile case.

The mother-of-five, whose plight has prompted prayers from the Vatican, has been on death row since she was convicted in 2010 of committing blasphemy during an argument with a Muslim woman over a bowl of water. She was placed in solitary confinement last week at the women's prison in the city of Multan, an official there told AFP.

Blasphemy is a hugely sensitive issue in Pakistan. The country has never executed anyone on the charge — but anyone convicted, or even just accused, of insulting Islam risks a violent and bloody death at the hands of vigilantes. Last year a British-Pakistani citizen who had been sentenced to death for blasphemy was shot and wounded by a guard at Rawalpindi's Adiala jail.

And a Christian labourer and his wife were burned alive last November after being accused of throwing pages of the Koran in the garbage. "She (Bibi) could be killed by any inmate or even a prison guard, so we have to be careful," a prison official told AFP.

A second official confirmed that Bibi had been isolated, adding: "We are concerned for her life." The second official, who spoke to AFP on condition of anonymity, said Bibi's health had deteriorated. Rights activists and family sources also voiced concerns for Bibi's health and said she suffers from asthma.

"Her life is in danger because of her health and the filthy prison conditions, and from fundamentalist elements within the prison," Shamaun Alfred Gill, a Christian activist and spokesman for the All Pakistan Minorities Alliance (APMA), told AFP. He said the group had repeatedly requested Bibi be transferred to a hospital, but the requests had been rejected. "Asia has a history of asthma and we were told that her health condition had worsened at one time but she was recovering now," a source close to the prisoner's family told AFP.

Bibi denies the charges against her. The Supreme Court agreed in July to hear an appeal against her sentence, but no date has yet been set. The allegations against her date back to 2009, when she was asked to fetch water while labouring in a field but some Muslim women objected, saying that as a non-Muslim she was unfit to touch the water bowl. A few days later the women went to a local cleric and made the blasphemy allegations.

In April, Pope Francis met with her husband and daughter and said he was praying for her. In 2010, his predecessor Benedict XVI publicly called for Bibi's release. Bibi is being held in a cramped, windowless cell in a high security zone of the prison, where other death row inmates are confined, the prison official told AFP this week.

The official, who said she has come into contact with Bibi several times while serving her food, said she appears withdrawn. "I found her either staring at the floor or coughing," she said, adding prison officials were reluctant to come into contact with the dishes Bibi used for fear of contracting her illness.

At one point, she said, Bibi was temporarily allowed to prepare her own food after she refused to eat prison meals fearing that officials would try to poison her. Bibi's husband has written to President Mamnoon Hussain to ask for her to be pardoned and allowed to move to France. Critics including European governments say Pakistan's blasphemy laws are often misused to settle personal scores. Christians make up around 1.6 per cent of the country's 200 million people.