Five Nordic countries issued a joint appeal to Iran Thursday, calling on the Islamic republic to commute the sentence against a woman condemned to death for adultery.

"We have closely followed the case of Ms. (Sakineh) Mohammadi-Ashtiani who was at risk of execution by stoning for adultery and may now be executed by hanging," said the statement from Denmark, Finland, Iceland, Norway and Sweden.

"Both sentences are clearly unacceptable. We state our strong opposition to the death penalty under all circumstances," it added.

"We appeal to the Iranian authorities to convert her sentence"

Fears earlier this week that Iran was about to execute Sakineh Mohammadi-Ashtiani provoked an international outcry, with Britain and France among the countries calling on Iran to call it off.

Iran retorted on Wednesday that she was in perfect health and that her case was still being reviewed, accusing the West of "shamelessly" trying to pressure it over the case by turning it into a human rights issue.

The joint statement from the Nordic countries was agreed at a Nordic Council meeting of the countries' foreign ministers in the Icelandic capital Reykjavik. Sweden's foreign ministry released a copy on Thursday.

The statement noted that they were also aware of several other similar cases.

"We express our deep concern about the human rights situation in Iran, including the crackdown on human rights defenders and reports of excessive use of force, arbitrary detentions, unfair trials and allegations of torture.

"The increasing number of executions is of particular concern."

Mohammadi-Ashtiani was sentenced to death by two different courts in the northwestern city of Tabriz in separate trials in 2006.

A sentence to hang for her involvement in the murder of her husband was commuted to a 10-year jail term by an appeals court in 2007.

But a second sentence, to die by stoning, was on a charge of adultery levelled over several relationships, notably with the man convicted of her husband's murder. That was upheld by another appeals court the same year.