Germany's Foreign Office said it was summoning the Iranian ambassador on Tuesday following the closure of two German-linked language schools in Tehran.
Iran's judiciary said the the branches were closed because of "illegal activities and financial fraud", Mizan news agency reported. Photos showed signs outside a branch of the German Language Institute of Tehran, which has links with the German embassy, being removed.
"Additionally, there have been reports of violations by other Germany-affiliated centres and investigations in this matter are ongoing," Mizan said.
Germany said there was no justification for the closures, which will leave many without qualifications or schooling. It planned to summon the Iranian ambassador to discuss the matter, a statement on Tuesday evening said.
"Language exchange forms the foundation of mutual understanding. The institute is a well-known and well-loved place of encounter where people go to great lengths to promote language learning amid challenging conditions," the Foreign Ministry said, calling for the institute to be allowed to resume teaching.
In 1995, Iranian authorities shut down Tehran’s Goethe International Institute, which was part of more than 100 sites around the world promoting German culture, language and education.