Here is a vivid, troubling documentary that reconstructs how Chinese activists hijacked the airwaves of state TV in the northeastern city of Changchun in March 2002. The group were followers of a banned spiritual practice called Falun Gong, labelled an “evil cult” by the ruling Communist party.

Watching archive footage of a Falun Gong gathering, it’s hard to see what all the fuss was about: hundreds of followers in a public square silently practising sequences of gentle movements; it looks like a tai chi class. But Falun Gong’s growing popularity spooked the government, enough to outlaw the group in 1999. On the night of the TV hijacking, followers replaced the teatime news with a pro-Falun Gong message.

The film is structured like a conventional documentary by Canadian director Jason Loftus. He follows 47-year-old comic-book artist Daxiong – real name Guo Jingxiong – as he visits the hijackers, who are now living in exile in America and South Korea. As they talk, Daxiong sketches. And, like the Israeli war movie Waltz with Bashir, his extraordinary drawings come to life in 3D (with the help of animation director David St-Amant). The hijacking plays out like a heist movie, noirish and stylised like a comic book.

Daxiong was himself a member of Falun Gong in Changchun. He disagreed with the hijacking at the time, knowing it would result in followers being persecuted, so he didn’t take part. Daxiong fled China in the early 2000s during the crackdown on the group after the hijacking, and lives in Canada. His views about the hijacking shift as he talks to the gang, who were arrested, tortured and imprisoned – and still live with the trauma.

Oddly, the film doesn’t mention the recent controversy surrounding Falun Gong’s right-wing links in the US. Still, this is a painful, important film, made more urgent in light of China’s tightening of religious freedoms and human rights abuses against Uyghurs and other Muslims.

• Eternal Spring is released on 21 October at Bertha DocHouse, London.