Bibi's lawyer has said his client was arrested after Muslim women told a cleric in a village in the eastern Punjab province that she had made "derogatory remarks" about the Prophet Muhammad.

A Christian woman on death row in Pakistan for blasphemy has been put in solitary confinement over fears of attacks by vigilantes enraged over a high-profile ruling in a separate blasphemy case that moderates said struck a blow against religious extremism in the country.

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 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.

Bibi's lawyer Sardar Mushtaq has said his client was arrested after Muslim women told a cleric in a village in the eastern Punjab province that she had made "derogatory remarks" about the Prophet Muhammad. He said the trouble began when the women objected to Bibi using their drinking glass because she was not a Muslim, setting off a heated verbal exchange.

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. She was placed in solitary confinement last week at the women's prison in the city of Multan, an official there told Agence France-Presse.

The move came 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 Punjab province governor Salmaan Taseer, who sought blasphemy law reform in a separate, high-profile case.

Qadri, who allegedly shot Taseer 28 times, later admitted to the killing, saying he objected to the politician's calls to reform blasphemy laws. Taseer had also been vocal in his support of Bibi.

Blasphemy is a hugely sensitive issue in Pakistan. The country has never executed anyone on the charge — but anyone convicted, or even accused, of insulting Islam risks a violent and bloody death at the hands of vigilantes. Critics including European governments say Pakistan's blasphemy laws are often misused to settle personal scores.

Christians, who make up around 1.6 percent of the country's 200 million people, are often discriminated against and marginalized by the Muslim majority.

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 laborer 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.

"She was vomiting blood last month and was having difficulty walking," the official said, adding that Bibi had been diagnosed with hepatitis B, a claim other officers did not confirm.

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 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 Pakistan's President Mamnoon Hussain to ask for her to be pardoned and allowed to move to France.

Wire services