Pair held hostage to stop anti-stoning campaign.
Mina Ahadi, chairwoman of the International Committee Against Execution and Stoning, reported Tuesday that the wife, Fereshteh Halimi, and brother-in-law, Farhad Halimi, of Mohammad Mostafai are being detained in Evin prison.
Ahadi said Mostafai's father-in-law was contacted by officials Monday and told both of his children would be freed in exchange for Mostafai.
Mostafai represents Sakineh Mohammadi-Ashtiani, 43, who was sentenced to die by stoning for adultery. Ashtiani's children have supported their mother and helped to fuel an international reaction of large proportions this month.
A website, freesakineh.org, had 137,814 signatures as of 8 p.m. Tuesday calling on Iran to release Ashtiani. The sudden uproar prompted Iran to announce earlier that she would not be stoned to death. But she remains in prison in Tabriz and subject to execution by hanging.
Radio Farda reported that human rights groups have so far organized public rallies on Ashtiani's behalf in 32 countries, including Brazil, Britain, France, Georgia, Germany, Italy and Sweden.
The Guardian of Britain reported last week that a source close to Ashtiani's family had told the newspaper she was under pressure in prison to silence the global campaign.
The Guardian said prison officials were demanding to know the names of those involved in the campaign for her release. It also quoted the source as saying, "Recently she was questioned and asked to advise her children to remain silent, otherwise they will be arrested too. International attention is the only hope for Sakineh's release."