BERLIN: Setting out to tell the story of Sarajevo's four-year siege in the 1990s, Nenad Sicin-Sain thought he was documenting Europe's last big war - only for Russia to invade Ukraine during filming, heightening the emotions of an already fraught project.

"Kiss the Future", which premiered at the Berlin Film Festival on Sunday, tells the story of the Bosnian capital's encirclement through the eyes of the artists and musicians who kept performing throughout, striking up an unlikely bond with Irish rock band U2.

"We started making a film on the last war in Europe and then a new war broke out," Sicin-Sain told reporters. "The story stayed the same but the emotions became more visceral."

Home to Muslim Bosniaks, Orthodox Serbs and Catholic Croats, Sarajevo was the most diverse of Yugoslavia's cities, and suffered the most when the country broke up, placed under siege by ethnic Serbs trying to carve out as large a slice of the country as possible.

Through interviews with artists, aid workers and U2 lead singer Bono, the film remembers the city's isolation, until artists hit on the idea of bringing the city's plight to world attention via telecasts into U2's stadium concerts.

It was the artists' resilience that attracted producers Matt Damon and Ben Affleck to the project.

"It's about the resilience of all of us and that's a wonderful thing to put out into the world, particularly now," Damon told Reuters. His production company is in the early stages of researching a film about the war in Ukraine, he added.

Footage of Bosnian Serb general Ratko Mladic - now serving a life sentence for genocide - denying war crimes makes the parallels with today's war inescapable.

"Everything that happened 30 years ago is so strongly and deeply connected to events that are happening today," said Vesna Zaimovic, a Sarajevan who helped make the documentary.

Scenes of Sarajevans performing punk rock in cellars as rockets rain down above bring to mind Kyiv's flourishing theatre scene, and the parallel is made explicit in the final frames when footage from last year of Russian President Vladimir Putin addressing a war rally is shown.

The film presents U2's 1997 post-siege concert in Sarajevo, where Bono urged the city to look with hope to the post-war and "kiss the future" as a moment of catharsis, but it also serves as a reminder of how long recovery can take.

To this day, the city has yet to host a larger concert.