Iranian authorities have banned documentary filmmaker Mojtaba Mirtahmasb — who co-helmed underground movie “This Is Not a Film” with Jafar Panahi — from traveling outside the country, according to the film’s international distributor.

Mirtahmasb had his passport pulled Monday at Tehran Airport where he intended to board a flight to Paris with his wife and son, said Clementine Hugot, head of Gaul’s Wide Management sales company. His family were allowed on the plane.

The purpose of the trip was to promote the French theatrical release of “This Is Not a Film,” before flying on to the Toronto Film Festival where it will unspool in the Masters section. Pic is also due to segue to fests in New York, London and Busan.

Mirtahmasb’s baggage, including his laptop and notebooks, was confiscated.

“We are very worried about the situation,” Hugot said.

Mirtahmasb was allowed to attend the Cannes Film Festival in May for the world preem of “Not a Film,” which was shot almost entirely in Panahi’s apartment on digital video and an iPhone for just $4,500. Dedicated to all Iranian filmmakers, it was smuggled to France on a USB thumb drive hidden inside a cake.

Iranian authorities are likely to have been aware that the film was in Cannes when Mirtahmasb flew there.

Pic, billed as “an effort” by Panahi and Mirtahmasb, chronicles a day in the life of Panahi who is under house arrest after being found guilty of defying the Iranian regime in December by backing the opposition.

Panahi — known for making films critical of Iran’s government, such as “The Circle” — has been banned from directing and producing films for 20 years.