Iranian authorities have detained Reza Khandan, the husband of prominent jailed human rights lawyer Nasrin Sotoudeh.
Khandan's arrest early on September 4 comes just hours after he raised concerns in a Facebook post about human rights violations in Iran, including the imprisonment of human rights defenders and the prosecution of women who have campaigned against the Islamic hijab.
Khandan has publicly campaigned for the release of his wife, who was arrested in June. A source who did not want to be named told RFE/RL's Radio Farda that charges against Khandan include acting against national security and promoting "anti-hijab" activities.
Amnesty International called on Iranian authorities to "immediately and unconditionally" release both Sotoudeh and Khandan.
"First the authorities jail Nasrin Sotoudeh on bogus charges, then harass, intimidate and threaten her family and friends, and now arrest her husband," said Philip Luther, Amnesty International's research and advocacy director for the Middle East and North Africa.
"These callous actions illustrate the lengths to which Iranian authorities will go to silence human rights lawyers, even targeting their families," Luther said in a statement on September 4.
Sotoudeh is currently being held in Tehran's Evin prison, where she started a hunger strike on August 25 in protest at her unjust detention and the authorities' pressure on her relatives and friends.
Sotoudeh's hunger strike was announced on the Facebook page of her husband.
Authorities arrested Sotoudeh, 55, on June 13 to serve a five-year sentence issued against her in absentia in September 2016 for allegedly carrying out "activities against national security in collaboration with domestic and foreign antirevolutionary elements," according to Human Rights Watch.
International rights groups and the U.S. government have denounced the arrest of the lawyer, who earlier in 2018 represented several women detained for publicly protesting the compulsory hijab.
Sotoudeh's lawyer said earlier this month that she had also been accused of espionage on top of the other charges.
Sotoudeh -- the co-winner of the European Parliament's 2012 Sakharov Prize for Freedom of Thought -- has denied all charges against her.
As outspoken critic of the Iranian establishment, Sotoudeh previously has spent several years in prison on security charges, including acting against Iran's national security. She has defended journalists, rights activists, and juveniles.