Dozens of European and German film industry reps gathered for a vigil Tuesday outside the Russian Embassy in Berlin to protest the imprisonment of Ukrainian filmmaker Oleg Sentsov and demand his immediate release.

Sentsov, a vocal opponent of Ukraine’s former pro-Russian government and of Russia’s annexation of Crimea, has been held by Russia for more than four years. He was convicted by a military court of terrorism in a trial described by Amnesty International as unfair.

Attendees at the vigil in Berlin held yellow signs saying “Free Oleg Sentsov.” The European Film Academy, which organized the event, issued a grave appeal: “Do not let Oleg die!”, alluding to the fact that the filmmaker has been on a hunger strike in prison since May 14.

Sentsov participated in the 2013 protests in Kiev that brought down the pro-Russian government of former Ukrainian President Viktor Yanukovych. Several months later, in May 2014, he was arrested at his home in the Crimean city of Simferopol in May 2014 by Russia’s Federal Security Service (FSB) following the country’s annexation of the peninsula. He was taken to Moscow and detained for more than a year before being found guilty by a military court of terrorist crimes and sentenced to 20 years in prison.

Russian government authorities have dismissed calls for Sentsov’s release, saying he was justly tried and convicted.

The filmmaker has told family and friends that he is prepared to die in his effort to win the freedom of 64 Ukrainian political prisoners held in Russia. Sentsov’s imprisonment and hunger strike have overshadowed the World Cup soccer tournament, which is being held in Russia. Tuesday’s somber vigil in Berlin offered a stark contrast to the city’s festive World Cup fan mile at the Brandenburg Gate, just a stone’s throw from the Russian Embassy.

“This is a silent vigil to remind people, even the people on the street but also the officials in the Russian Embassy who can see us through their windows, that the life of a citizen, of an artist, is in severe danger,” European Film Academy Director Marion Döring told Variety. “We can only hope until the last moment that he is released.”

Döring added that Sentsov’s release would ultimately depend on “high-level negotiations at the political level.”

“We are not politicians. We cannot sit down with [Vladimir] Putin and convince him to release Oleg, but we hope that through negotiations on a political level, he will be freed,” she said. “We are doing this to help people who have been denied their freedom. The Russians know this; they see it. We hope it will move Putin to release him.”

Also attending Tuesday’s vigil were Berlin Film Festival curator Thomas Hailer; filmmaker Dani Levy; actress Meret Becker (“Tatort”); actor Gustav Peter Wöhler; writer-producer Fred Breinersdorfer; and Ben Gibson, director of the German Film and Television Academy in Berlin.

“We have been on this case for many years and working closely with the European Film Academy,” said Hailer, noting that the Berlinale last year screened the documentary “The Trial: The State of Russia vs. Oleg Sentsov.”

“We have to keep it going. Oleg is a very brave man. He’s being held in a Siberian gulag, where they try to break a person’s will. He’s innocent; he hasn’t done anything. The accusations are made up.”

At the Karlovy Vary Film Festival last week, the Film Academies Network of Europe also called for Sentsov’s immediate release, saying the filmmaker was “in severe danger” owing to his hunger strike.

European Council President Donald Tusk likewise appealed for Sentsov’s release in his opening speech of the recent G-7 summit. The European Parliament and other international leaders have echoed the call.

On Monday, the Rotterdam Film Festival, which premiered Sentsov’s “Gamer” in 2012, said it would share the film on its pay-per-view streaming platform, IFFR Unleashed, and donate 100% of the revenue to supporting the filmmaker’s case.