YouTube said in a blog post Thursday over the past week it had already shut off comments for tens of millions of videos that could be subject to predatory behaviour.

Now, it will expand that to suspend comments on virtually all videos featuring children, as well as videos featuring older kids that "could be at risk of attracting predatory behaviour".

In a tweet, YouTube CEO Susan Wojcicki linked to the update and explained the change: "Recently, there have been some deeply concerning incidents regarding child safety on YouTube. Nothing is more important to us than ensuring the safety of young people on the platform."

According to YouTube, a "small number of creators" with videos featuring children will be able to keep comments enabled.

However, YouTube said, it will require those channels to actively moderate their comments and "demonstrate a low risk of predatory behaviour."

The problem was exposed last week by vlogger Matt Watson, who discovered YouTube's algorithms enabled child predators to secretly connect across a series of videos with young girls engaged in everyday activities like gymnastics, stretching or simply hanging out at home.

As documented in his February 17 video, members of what Watson called a "soft-core pedophilia ring" made sexualised comments about the girls tagged with time-stamps identifying moments when the kids were in certain poses.

News of the child-predator comments led marketers including Disney, AT&T, Epic Games, Hasbro, McDonald's and Nestle to suspend their advertising on YouTube.

In addition to disabling comments on videos with kids, YouTube said it is developing an "even more effective classifier" designed to better identify and remove child-predator comments.

The new system is "more sweeping in scope" than YouTube's previous comment-scanning tool and will detect and remove twice as many individual comments, according to YouTube.

Australian Associated Press