Update: Iran: Sakineh Mohammadi Ashtiani could be Hanged in Iran'

An Iranian woman whose sentence of death by stoning for adultery provoked an international outcry could be executed by hanging instead, the country's judicial authorities have indicated.

Sakineh Mohammadi Ashtiani, a 44-year-old mother of two, was convicted of conducting an "illicit relationship outside marriage" in 2006 and has since been kept in Tabriz prison in the west of Iran.

Malek Ajdar Sharifi, the head of the judiciary in East Azerbaijan, said on Sunday that the prison does not have the "necessary facilities" to carry out the sentence of stoning. Therefore, he said, authorities are considering hanging as an alternative.

According to Sharifi, an investigation has been launched to determine whether it is legally and religiously possible to go ahead with the hanging instead of stoning. "As soon as the result of the investigation is obtained, we will carry out the sentence," he said in quotes carried by the semi-official Isna news agency.

Mohammadi Ashtiani's sentence was temporarily halted in response to international protests, and Iranian officials have since made confusing and often contradictory comments about her fate. In 2010 President Mahmoud Ahmadinejad denied she had been given a sentence of stoning, while a senior adviser to Iran's supreme leader, Ali Khamenei, signalled her life could be spared.

Mina Ahadi, a member of the International Committee against Stoning, said Sharifi's remarks proved that international pressure had succeeded, but warned that execution was still a real possibility.

"Iran kept quiet about Sakineh for almost a year and we had little information about her case and now … they have suddenly stepped forward to say she could be hanged," she said. "I believe they are testing the water."

Mohammadi Ashtiani's case came to prominence in July 2010 when her children appealed to the international community to help stop the imminent execution of their mother.

Within days hundreds of human rights activists, campaigners and world leaders joined an international campaign for her release and Mohammadi Ashtiani soon became the symbol for those facing the punishment of stoning in Iran.

Seven people have been stoned to death in Iran since 2006 and at least 14 are currently facing death by stoning, according to the NGO Iran Human Rights.

At her trial Mohammadi Ashtiani was also given a 10-year prison term for the murder of her husband, which her lawyer said was subsequently reduced to five years for "complicity" in the crime, according to Amnesty International. Many activists believe her convictions were based on confessions made under duress.

Mahmood Amiry-Moghaddam, a spokesperson for the NGO Iran Human Rights, said Iran has a history of changing stoning sentences to hanging in face of pressure. "One such examples is that of Abdollah Farivar, a music teacher who was sentenced to death by stoning for adultery but was instead hanged in 2009," he said. He added that changing stoning to hanging is illegal under Iranian law.

Several people have fallen victim to the Iranian authorities for highlighting Mohammadi Ashtiani's case. Mohammad Mostafaei, one of her lawyers, was briefly arrested and later forced to flee. He now lives in Norway.

Houtan Kian, Mohammadi Ashtiani's other lawyer, who was appointed by the government, is in jail after being arrested in October 2010 for speaking to the media. Kian, who is reported to have been tortured, has been held incommunicado for more than a year. Last December, he was forced to make a televised confession along with Mohammadi Ashtiani, her son and two German journalists who were detained for interviewing Mohammadi Ashtiani's family without a press visa.

The confessions, were broadcast by Iran's English-language Press TV, which has its main overseas offices in London.

In recent years, Iran has been criticised for the sharp rise in its executions. Earlier this month, Amnesty International called Iran's escalating use of the capital punishment "a killing spree of staggering proportions". At least 600 people were executed in Iran in 2011, up to the end of November.