China will restrict broadcasts of the 93rd Academy Awards next week because a short documentary about the 2019 Hong Kong anti-government protests received a nomination.

Norwegian director Anders Hammer spent a year in the city filming the low budget 35-minute movie. China's censorship efforts have given the documentary a free advertising boost.

"We are part of a category, short documentaries, which is not normally one that gets most attention," Hammer said. "It's ironic Beijing is actually at this point promoting our documentary."

In China, state news media have been told not to broadcast the awards ceremony live April 26.

The name of the documentary - "Do Not Split" - is taken from a protest motto for unity in the face of China's attempts to muzzle the 2019 Hong Kong pro-democracy movement.

Hong Kong residents turned out in thousands that summer to protest a proposed extradition bill that would have allowed the government to send people to trial in China's opaque judicial system.

"It was the biggest revolt against Beijing and (its) political leadership in a very long time," the director said. "I think that they were very afraid that this could spread in some way and that you would see similar actions being taken in mainland China."

The documentary followed aspiring teacher turned student activist Joey Siu - who has since fled the city for fear of prosecution. She helped to organize campus protests and street marches which frequently turned into violent clashes with riot police.

By the end of 2019, police officers had fired more than 16,000 tear gas rounds and 10,000 rubber bullets into crowds - as well as several rounds of live ammunition.

"All of us understand that this is going to be a very long and very difficult battle so we are trying our very best to sustain the momentum that we built in 2019," Siu said.

"We understand that the situation in Hong Kong is not going to become any better and we're pretty sure that the Chinese Communist Party isn't planning to restore any kinds of freedom or rights that we used to enjoy."