Turkish producer Cigdem Mater, known on the festival circuit for backing arthouse titles such as the 2013 Venice competition drama “Sivas,” has been arrested and sentenced to 18 years in prison on trumped-up charges, along with other activists, in connection with the 2013 Gezi Park anti-government protests.

Mater, who is also a journalist, was incarcerated on Monday in Istanbul at the conclusion of a trial during which Turkish philanthropist Osman Kavala, who was already in custody, was sentenced to life imprisonment on charges of “attempting to overthrow the government” of Turkish President Recep Tayyip Erdogan by allegedly financing the protests.

Mater and six other activists are accused by the Turkish court of supporting Kavala and being behind the protests that were prompted by construction of a mall in an Istanbul park. The protests snowballed and grew into nationwide anti-government unrest. Mater is also specifically accused of trying to raise financing for a documentary about the Gezi Park movement that was never made.

The Istanbul court ordered Mater and the other activists who were not in custody to be immediately arrested, the state-run Anadolu Agency reported. Mater was arrested on Monday and sent to Istanbul’s Bakirkoy women’s prison after the verdict was announced.

Kavala, Mater and all other defendants have repeatedly denied the accusations. They are expected to appeal the verdict.

Mater came to Turkey from Germany in February to attend the trial in Istanbul.

The verdict, which has been vehemently slammed by European and U.S. diplomats, is expected to further strain Turkey’s ties with Western countries. Europe’s top human rights body, the Council of Europe, has initiated infringement procedures against Turkey for refusing to abide by a 2019 ruling by the European Court of Human Rights that called for Kavala’s release on grounds that his rights had been violated.

Amnesty International called the ruling a “devastating blow” for human rights, saying that the court’s decision “defies all logic.” The human rights group PEN America is calling it a “dark moment for Turkey.”

News of Mater’s arrest is also starting to reverberate in the international film community. Turkish producer Nadir Operli, who is a member of the European Film Academy, has launched an appeal for “solidarity with Cigdem Mater and all co-defendants, and protest this unlawful trial,” he said in an email.

Several other members of the Turkish and international film community are speaking out on social media in an effort to drum up international support, including the team of 2015 female empowerment drama “Toz Bezi” (“Dust Cloth”) by Ahu Ozturk, about two Kurdish cleaning women working in Istanbul’s outskirts, which won prizes at Turkish festivals.

Mater, besides being a co-producer on Kaan Mujdeci’s “Sivas” and “Dust Cloth,” is an associate producer of Seren Yuce’s “Cogunluk” (“Majority”) and worked as a line producer on international projects shot in Turkey including Ai Weiwei’s “Human Flow.”