Queensland Police said they were aware of the tape but did not confirm whether it showed Gareth and Stacey Train.

The couple, along with Gareth's brother Nathaniel, were killed by police after shooting two officers and a neighbor.

Police are looking into the trio's links to conspiracy theories.

Officials said the suspects used "many weapons", but are yet to reveal what kind — or any motive for the attack.

But Prime Minister Anthony Albanese on Thursday said it was a "vicious and deadly ambush". The Queensland Police union boss Ian Leavers claimed the property was set up with a sophisticated surveillance system and a stockpile of guns and ammunition.

In videos uploaded to a YouTube account - first reported by local media outlet Crikey on Friday morning - a pair sharing the likeness of Gareth and Stacey rail against police.

On the account, which has since been deleted, they use the names Daniel and Jane. Crikey and other local outlets have reported they are Gareth and Stacey's middle names.

The BBC has verified the existence of the YouTube account using internet archives, but not the identity of its owners.

The most recent video appears to show Gareth, 47, and Stacey, 45, shrouded in darkness, admitting to the killings. The man refers to "devils" and "demons".

The video was published at 19.39 on Monday, three hours after four officers arrived at the property in Wieambilla - 270km (168 miles) west of Brisbane - and were met with a hail of bullets.

Two constables - Matthew Arnold and Rachel McCrow - were killed, as was 58-year-old Alan Dare, a neighbor who turned up at the house concerned it was on fire.

After a six-hour standoff, specialist police shot and killed the three suspects.

Gareth's brother and Stacey's ex-husband, Nathaniel Train, is the missing man police were at the property to check on. He does not feature in the video.

In a statement, Queensland Police said it would be "inappropriate" to comment on the video while the "complex and thorough" investigation is underway.

Queensland Police Commissioner Katarina Carroll has previously said the investigation will look into the suspects' online activity.

"We're definitely investigating every avenue - whether it be premeditated, some of the stuff that's online from these people," she said.

On Thursday, Home Affairs Minister Clare O'Neil said radicalization was likely to have played a role in the shooting.

"Radicalisation is not new. But... conspiracy theories, disinformation and misinformation - problems as old as time - are being turbocharged by technology into terrible acts of violence," she told parliament.