Shafagh Rahmani told RFE/RL’s Radio Farda on August 14 that her husband was arrested on August 11, and that authorities told her he faces "unspecified charges in connection with his activities."

Rahmani said it wasn’t clear which state body had ordered the arrest.

"My husband was granted British citizenship 25 years ago but has been living in Iran in the past fifteen years," she told Radio Farda.

Rahmani first reported her husband’s arrest in an Instagram post on August 13, where she said that a court at Tehran’s Evin prison had issued an order for his detention for one month.

Ahmady is known for his research on female genital mutilation in Iran. He’s also done research on child marriages as well as temporary marriages in the Islamic republic.

Iranian and British authorities have not publicly commented on Ahmady’s arrest, which comes amid tensions between Tehran and London over the seizure of a British-flagged tanker by Iran's Islamic Revolutionary Guards Corps (IRGC) for alleged marine violations.

The move came following Britain's seizure of an Iranian oil tanker near Gibraltar on suspicion of violating EU sanctions against Syria.

Ahmady took global campaigners by surprise in June 2015 when he published a study suggesting tens of thousands of Iranian women have undergone female genital mutilation (FGM.)

Before Ahmady's disclosure, Iran was not recognized as a country affected by FGM - an ancient ritual which is internationally condemned as a serious rights violation.

But Ahmady's research, based on 4,000 interviews, showed FGM is also performed in "secret pockets" of four Iranian provinces; West Azerbaijan, Kurdistan and Kermanshah in the west, and Hormozgan in the south, Reuters reported at the time.

Ahmady's research work includes five books and three short ethnographic documentaries, made in various regions of the world, including Iran.

In recent years, several Americans and dual nationals have been jailed in Iran on alleged espionage charges.

Iranian authorities have not provided any solid evidence to back their claims.

Among those jailed is Xiyue Wang, a Princeton University student, who has been sentenced to 10 years in jail for espionage. He was arrested in August 2016 while conducting research for his dissertation on Iran's Qajar dynasty. Both Wang and the university deny the claims.

Last month, the French Foreign Ministry called on Tehran to allow consular access to Fariba Adelkhah, an anthropologist and author of several books on Iran, who had been reportedly detained in June on unknown charges.