The award-winning Iranian film maker Jafar Panahi has been detained in Tehran, his wife and local media say.
Mehr news agency reported that he was held after going to Evin prison to ask prosecutors about Mohammad Rasoulof, one of two fellow directors arrested last Friday for supporting protests.
Mr Panahi's wife told BBC Persian he was informed by guards that he had an outstanding prison sentence to serve.
Tahereh Saeedi said his detention amounted to an unlawful "kidnapping".
"Jafar has some rights as a citizen. There's due process. To imprison someone, they need to be summoned first. But to imprison someone who is protesting outside the jail raises a lot of questions. This is a kidnapping."
Mr Panahi was held a day after signing a joint statement calling for his two colleagues' release.
Mr Rasoulof and Mostafa Al-e Ahmad were arrested over social media posts concerning the collapse of a 10-storey building in the city of Abadan in May that killed more than 40 people. They urged security forces to "put down your guns" and not prevent protests over the disaster. The protesters blamed it on "incompetent officials" and called for them to be punished.
The two film makers were accused of "inciting unrest and disrupting the psychological security of society", state news agency Irna reported.
The outspoken reformist politician and former deputy interior minister, Mostafa Tajzadeh, was also arrested in Tehran on Friday suspicion of "acting against national security", according to state media.
"We condemn the suppression and the pressure that independent film makers and free thinkers are experiencing," said the statement signed by 334 Iranian film makers and activists, which Mr Panahi posted on Instagram.
"We also condemn the systematic violation of the basic individual and social rights by the relevant organisations and institutions."
Mr Panahi, 62, has won many awards at international film festivals. They include the Berlin International Film Festival's top prize, the Golden Bear, for Taxi in 2015, as well as the Best Screenplay prize at Cannes Film Festival for Three Faces in 2018.
In 2010, he was arrested for supporting mass anti-government protests that erupted after the previous year's disputed presidential election. He was later convicted of "propaganda against the system" and sentenced to six years in prison and banned from making movies or travelling abroad for 20 years.
The Cannes festival said in a statement on Monday that it "strongly condemns these arrests as well as the wave of repression obviously in progress in Iran against its artists".
"The festival calls for the immediate release of Mohammad Rasoulof, Mostafa Al-e Ahmad and Jafar Panahi," it added.
The Berlin festival said on Saturday that it was "dismayed" to learn about the arrests of Mr Rasoulof - who won the Golden Bear for There is No Evil in 2020 - and Mr Al-e Ahmad.