The video, which has attracted 56,000 views, has been condemned by police, community leaders and observers who have labelled the filming and uploading of an act of self-harm as "deplorable", "nasty" and "disgusting".

Three identical versions of the video were still online Thursday morning after dozens of complaints but had been prefaced by content warnings asking viewers if they wanted to proceed.

The footage, believed to be filmed at Belconnen skate park, showed young people arguing with an older, shirtless man who produced a knife and asked whether they had seen someone stab themselves.

"I dare you to stab yourself, I dare you to stab yourself," said one bystander.

The words "you're a bitch mate, do it, do it" can also be heard.

The man, who is understood to have serious mental health issues, turned his arm palm-upward, rested it flat across a railing, raised the knife and forcefully stabbed himself in the forearm with a knife, which had a blade several centimetres long.

There were shocked noises from onlookers – many of whom were laughing even though the man had injured a part of his body – and a number of them immediately started taking photos and videos.

ACT Policing, who attended on the night, described the actions of the teenagers as "deplorable".

Police said posting the videos on YouTube was "completely inappropriate", and said members of the public should report such content to police and to YouTube.

A police spokesman said officers identified criminal offences on the night, but couldn't comment further because the matter was currently before the court.

They urged Canberrans to instead call police when someone is threatening to self-harm or self-harming.

The footage has been online for four months and – apparently – has not garnered enough complaints about violent content to be taken offline even though it has attracted tens of thousands of viewers.

One of Communications Minister Malcolm Turnbull's staffers used YouTube's flagging system to report one of the videos when told about the publicly available footage on Tuesday morning.

YouTube tells users it is "not a shock site".

"Don't post gross-out videos of accidents, dead bodies and similar things," it warns, although videos are not automatically taken down once a report by a viewer has been lodged.

The Canberra Times flagged the videos as displaying violent, repulsive or inappropriate content more than 20 times from separate accounts on Tuesday, Wednesday and Thursday. Additionally, it contacted the press offices of YouTube and owner Google to draw their attention to the video and asked how many times it had been flagged by users.

In response a YouTube spokesman said: "We count on our community members to know the Guidelines and to flag content they believe violates them. We review flagged videos, and if we find that they do violate the Guidelines, we remove them."

The person who posted the original video recently complained to another person who apparently re-posted the images.

"I filmed this and edited it myself," the original poster said. "I have the original on my channel. This person does not own this video."

People responded by saying the footage was disgusting and not something to be proud of.

Chair of the Belconnen Community Council Robyn Coghlan said the video reflected people's capacity to be nasty.

She said it also was unfortunate an incident such as this happened at the Belconnen skate park, fast becoming one of the best destinations in Australia for skaters.

"It's disappointing – it's a valued resource designed for young people," she said.

Chief Minister Katy Gallagher encouraged those involved the video to seek appropriate assistance following the "really distressing" event.

"The video is really distressing for all involved and I would encourage both the man and others shown in the video or their parents or guardians to seek appropriate assistance from available support services," Ms Gallagher said.

She said she was confident ACT Health and the ACT Ambulance Service would have responded appropriately.

Human Rights Commissioner Tim Wilson said it appeared the video was recorded in a public setting and there were limited restrictions on recording in public.

"A formal complaint can also be lodged with the commission and it will be investigated, though the commission's legislative power is limited to breaches of human rights by the Commonwealth government," Mr Wilson said on Tuesday.

"It would be more appropriate to lodge a complaint with the police."

ACT Policing said it regularly monitors social media during investigations, and often receives links to content from the public.

"The co-operation of the community in bringing to police attention anti-social and criminal activity posted on social media is critical to effective community policing," a spokesman said.

Canberrans can call Crime Stoppers on 1800 333 000, police operations on 131 444, or send links to Canberra Connect via their website.

For help or information call Lifeline on 131 114, or visit beyondblue.org.au.