(CNN) -- Iran's government is denying reports that an Iranian woman convicted of adultery will be executed by stoning, though her death sentence may still be carried out by some other method.
In the Islamic republic's first public statement on the case of Sakineh Mohammedie Ashtiani, 42, the Iranian Embassy in London, England, said Thursday that "this mission denies the false news aired in this respect and ... according to information from the relevant judicial authorities in Iran, she will not be executed by stoning punishment.
"It is notable that this kind of punishment has rarely been implemented in Iran and various means and remedies must be probed and exhausted to finally come up with such a punishment," the embassy said.
But Ashtiani still faces the possibility of execution for her 2006 adultery conviction, said Drewery Dyke of Amnesty International in London.
"We have noted in the past that those who have been sentenced to stonings have gone on to be hanged," he said. "That remains a concern."
Dyke said Amnesty first heard that Ashtiani had been sentenced to death by stoning from her lawyer, Mohommad Mostafaei.
Dyke said he welcomed Iran's statement that appeared to back off from the punishment that some governments have condemned as barbaric, but added, "It raises far more questions than it answers."
Ashtiani's son, who appealed Wednesday to Iran's courts to spare his mother's life, said he won't accept any decision short of his mother's freedom. Through human rights activist Mina Ahadi, Sajjad Mohammedie Ashtiani said he would be satisfied only when Iran's judiciary officially drops the charges against her.
Ahadi has told CNN that only an international campaign designed to pressure the Islamic regime in Tehran could save Sakineh Ashtiani's life.
"Legally, it's all over," said Ahadi, who heads the International Committee Against Stoning and the Death Penalty, earlier this week.
Ashtiani's son wrote in an open letter to government officials that there was neither evidence nor legal grounds for his mother's conviction and sentence. He said the family has traveled six times from their home in Tabriz to Tehran to speak with Iranian officials, but in vain.
"So I have no option but reaching out to them this way," he said earlier in the week.
Why, he asked, has an accused been twice prosecuted on the same charge when Islamic criminal law allows prosecution only once?
Sajjad Ashtiani told CNN that he visits his mother every Monday in jail, never knowing whether that meeting will be their last.
She was convicted of adultery in 2006 and forced to confess after being subjected to 99 lashes, human rights lawyer Mostafaei told CNN. She later recanted that confession and has denied wrongdoing.
Her conviction was based not on evidence but on the determination of three out of five judges, Mostafaei said. She has asked forgiveness from the court but the judges refused to grant clemency.
Iran's supreme court upheld the conviction in 2007.
Meanwhile, the U.S. State Department on Thursday acknowledged reports of the planned stoning. Spokesman Mark Toner said, "We're deeply troubled by press reports of the planned execution by Iranian authorities of Sakineh Mohammadi Ashtiani by stoning.
"Stoning as a means of execution is tantamount to torture. It's barbaric and an abhorrent act," he said.
"We call on the Iranian authorities to live up to their due process commitments under the International Convention on Civil and Political Rights and we condemn in the strongest terms the use of the practice of stoning anywhere it occurs as a form of legalized death by torture."