The group said the attack was in response to, what they described as, Gold Coast police's "excessive force" at the Indigenous land rights protest on Friday, which saw in five activists arrested and charged.

In a statement posted with the video, the arsonists said the Commonwealth's "time is up" and called for more activists to travel to the Gold Coast and take part in further protests.

"We watched on social media as the police brutalised and arrested peaceful Stolenwealth Games protestors on the Gold Coast," the activists' statement read.

"They used excessive force on young people, people with disabilities, and elders.

"Allies are urgently needed at Camp Freedom on the last two days of the Commonwealth Games, to join peaceful protests and protect the camp.

"Our action is in no way endorsed by Stolenwealth Games organisers and protestors (who have no knowledge of it), but they have our solidarity through this and more practical acts.

"This surfboard clock was launched in 2015 on this fake beach to count down 1000 days until the Commonwealth Games. Time is now up for the Commonwealth, the state, and ... the police.

"This isn't the Queen's land. The time to decolonise is now, for healing the land and healing the people of the land."

A Queensland Police Service spokeswoman said officers were aware of the incident.

"Police are aware of a wilful damage incident involving a Commonwealth Games countdown clock at the South Bank Parklands. Investigations into the matter have commenced," police said.

"Police are urging anyone with information in relation to this incident to contact Crime Stoppers on 1800 333 000 on or Policelink on 131 444."

The surfboard clock was surrounded by metal barriers and the charred remains wrapped in black plastic on Saturday morning.

Gold Coast 2018 Commonwealth Games Corporation (GOLDOC) chairman Peter Beattie said he was “disappointed” with the torching and described the actions as an act of “stupidity”.

“I’m not going to pretend that I’m not disappointed about what happened to the South Bank clock,” he said.

“GOLDOC has been really clear that we respect people’s right to protest, whether we agree with
people or not. That’s a fundamental principle of democracy.

“I just think we’re a bit better than that as Australians.”

Commonwealth Games Federation chief executive David Grevemberg said the incident would do nothing to impact the Federation’s plans to continue to work towards Indigenous reconciliation.

“Many of us have engaged the protesters to really show our respect and listen and learn as well.

“The journey does not stop here in terms of Commonwealth-Indigenous reconciliation.

"There’s a huge amount of discourse. Watch this space over the next couple of years.”