Iran says it has arrested two "foreign nationals" who interviewed the family of a woman who was sentenced to death by stoning for adultery.
Iran's judiciary spokesman said the pair did not have the correct media accreditation to interview the son of Sakineh Mohammadi Ashtiani, 43.
At the same time, a German-based rights group said it feared Ms Ashtiani's son and lawyer had been arrested during an interview with two German journalists.
A reform website also carried the news.
Iran has temporarily suspended Ms Ashtiani's stoning verdict under international pressure, but says no definite decision has yet been made about her case.
Last month, reports surfaced that Iranian courts were instead considering hanging her for the murder of her husband.
Her lawyers insist she is innocent.
Iranian public prosecutor Gholam Hossein Mohseni Ejeie told local media that someone who was present during the interview contacted the authorities after becoming "suspicious about the manner of questioning" of the two foreigners.
He did not identify them or their nationalities.
"After conducting relevant investigations, it was established that these two people were not reporters and even if they were, they did not have the relevant documents."
Earlier in the day, the German-based International Committees against Execution and Stonings raised fears of possible arrests in the case.
Mina Ahadi, the group's founder, said she was on the phone with Ms Ashtiani's son Sajjad and her lawyer Javid Houtan Kian as they were being interviewed by journalists on Sunday.
"Suddenly one of the journalists shouted, 'What's happening', and then said he had to hang up," she told AFP news agency.
Ms Ahadi said she had had no news of the four men's whereabouts since then.
She said the two journalists were working for a German newspaper but refused to name them, citing security reasons.
Sakineh Mohammadi Ashtiani, a mother of two, was originally convicted in May 2006, when a criminal court in East Azerbaijan province found her guilty of having had an "illicit relationship" with two men following the death of her husband. She was given 99 lashes.
But that September, during the trial of a man accused of murdering her husband, another court reopened an adultery case based on events that allegedly took place before her husband died.
Despite retracting a confession she said she had made under duress, Ms Ashtiani was convicted of adultery and sentenced to death by stoning.
Officials suspended her stoning sentence in July, and reports of a murder trial then emerged.
The case has caused international outrage.