Pakistani court has upheld the death sentence of a Christian woman who was convicted for blasphemy in 2010 after a row with a group of Muslim women over a glass of water.

Asia Bibi, a 50-year-old mother of five, had appealed before the Lahore High Court against the ruling, in which she was found guilty of insulting Islam's Prophet Muhammad, but the court rejected her appeal Thursday, her lawyer said.

Sardar Mushtaq, a defence lawyer, said she would appeal to the country's Supreme Court.

"We have the right to appeal in 30 days, and we will continue this legal battle by approaching the Supreme Court of Pakistan," Mr Mushtaq said.

"We have a strong case, and we will try our best to save her life," he told The Associated Press.

Mrs Bibi 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.

He said the trouble began when the women objected to Mrs Bibi using their drinking glass because she was not a Muslim, setting off a heated verbal exchange.

Mrs Bibi's case drew global criticism in 2011 when Pakistan's minister for minorities Shahbaz Bhatti and eastern Punjab Governor Salman Taseer were killed for supporting her and opposing blasphemy laws.

Taseer was killed in the capital Islamabad by one of his police guards after visiting Bibi in jail.

Bhati was killed months later by the Pakistani Taliban, who called him an "infidel Christian."

International and local human rights groups have called for amending blasphemy laws introduced by the military dictator Muhammad Zia-ul-Haq in 1980s.

In a statement Thursday, Amnesty International called for Mrs Bibi's release.

"This is a grave injustice," said David Griffiths, Amnesty's Deputy Asia Pacific Director. He said there were serious concerns about the fairness of the trial.

"Her mental and physical health has reportedly deteriorated badly during the years she has spent in almost total isolation on death row. She should be released immediately and the conviction should be quashed," he said.

Under Pakistani blasphemy laws, insulting the Koran or the Prophet Muhammad can be punished with life imprisonment or death. Experts say the laws often are exploited for personal gain.

Pakistan imposed a moratorium on executions in 2008 and has never executed anyone convicted of blasphemy. Instead, such cases usually linger on appeal.