A new documentary has captured Edward Snowden's leak of National Security Agency documents as it unfolded in a Hong Kong hotel room.

Laura Poitras' highly anticipated documentary Citizenfour, which premiered at the New York Film Festival, presents a remarkably intimate portrait of Mr Snowden, including his first meetings with the journalists with whom he shared thousands of documents revealing the collection of Americans' phone and email records.

Initially communicating under the alias "citizenfour", Mr Snowden reached out to Ms Poitras, a hybrid journalist-documentarian, and Guardian reporter Glenn Greenwald. The film shows their first meeting with Mr Snowden and the days that followed as his revelations made international news.

From the beginning, Mr Snowden is seen as highly aware that such a leak would mean sacrificing his own freedom.

"I already know how this will end for me," he says. "And I accept the risk."

Mr Snowden was charged with three felony offences under the Espionage Act: unauthorised communication of national defence information; theft of government property; and wllful communication of classified communications intelligence to an unauthorised person.

He is currently living in asylum in Russia, where he fled from Hong Kong with the aid of WikiLeaks founder Julian Assange.

Ms Poitras said she showed the film to Mr Snowden two or three weeks ago, during which she shot footage (used in the film) of him and his long-time girlfriend Lindsay Mills cooking dinner at their Moscow home.

Members of Mr Snowden's family attended the screening, which was received with an emotional standing ovation. His father, Lonnie Snowden, told the crowd: "The truth is coming, and it cannot be stopped."

Citizenfour, which the Weinstein Co's boutique label Radius will release on October 24, had been shrouded in mystery.

For fear of having her footage seized, Ms Poitras edited the film in Berlin. She and Mr Greenwald returned to the United States earlier this year only after sharing the Pulitzer Prize for public service given to The Washington Post and The Guardian for the NSA revelations.

Citizenfour does not aim to be an unbiased documentary about a controversial figure, but rather seeks to depict the stealth build-up of government surveillance in the wake of the terrorist attacks of September 11 2001 and the people who have fought to uncover it.

"This was a film about people who take risks and come forward," Ms Poitras said after the screening.

Mr Snowden, a former contractor for the NSA, comes across as calm, intelligent and deliberate. There are glimpses of paranoia. After room service calls his hotel room, he unplugs the phone. A fire alarm momentarily prompts his concern. And when he enters passwords on his laptop, he covers himself with a red blanket.

Throughout the process Mr Snowden speaks about not hiding or "skulking around", instead certain of himself as a whistleblower ready to take sole responsibility for the leak.

"Put the target right on my back," he tells the film-makers.

"So much has been said about Edward Snowden: a lot of it bad, but a lot of it really good," Mr Greenwald said after the film. "I felt like this was really the first time that people could see who he really is in an unmediated way."