The documentary film "Bakur" ("North") was scheduled to open Sunday afternoon, but the showing was cancelled at the last minute after the organisers received a letter from the Turkish culture ministry saying the film didn't have the necessary registration certificate.

More than 100 filmmakers, including Ceylan who won the top prize last year for his epic drama "Winter Sleep", signed an open letter published in media Monday alleging "oppression and censorship" by the Turkish government.

"We, the undersigned filmmakers, oppose the imposition (of the rule) as a tool of censorship," the letter said, claiming the fact that the rule only applied to domestic films revealed a "political agenda."

They demanded that the festival halt all of its screenings

A total of 23 directors withdrew their films from the festival in solidarity, according to a count made from announcements on the official festival website.

The row prompted the online Radikal newspaper to cancel its annual "Radikal Peoples' Prize" for this year because "art, creativity and freedom of expression cannot exist in the presence of censorship."

"No one would like to live in country like this. We say 'no' to censorship, the state's intervention and an oppressed festival," Radikal said on its website Monday.

The documentary, directed by Cayan Demirel and Ertugrul Mavioglu, shows the daily life of male and female Kurdistan Workers Party (PKK) fighters and includes interviews with senior figures including the PKK's Iraq-based operational commander Cemil Bayik.

The government is in talks to end the PKK's decades-long rebellion for self-rule that has claimed tens of thousands of lives. But the scrapping of the screening comes a day after deadly clashes in the southeast that threaten the peace process.

The festival runs from 4-19 April and is the biggest cinematic event of the year in Istanbul.