A Taiwanese hacking group called Anonymous 64 has been carrying out cyberattacks against targets in mainland China, Hong Kong and Macau, China's national security ministry said on Monday, urging netizens to report cases of "anti-propaganda sabotage."

Since the beginning of this year, Anonymous 64 - which the ministry said belonged to Taiwan's cyber warfare wing - has sought to upload and broadcast "content that denigrates the mainland's political system and major policies," on websites, outdoor screens and network TV stations, it said in a blog post.

Taiwan frequently accuses Chinese groups of seeking to spread online disinformation or carry out cyberattacks across the democratically governed island. China claims sovereignty over Taiwan and has ramped up military and political pressure against over the past five years to assert its claims.

The hacking group's X account said it was set up in June 2023 and showed screenshots of efforts to broadcast videos likening Chinese President Xi Jinping to an emperor, marking the second anniversary of protests against Beijing's strict COVID curbs and commemorating the 1989 Tiananmen Square demonstrations.

One video was an address from an Anonymous 64 member wearing the Anonymous hacking group's Guy Fawkes mask in the style of the graphic novel and film V for Vendetta.

Neither the X site nor the blog post from China's national security ministry said whether Anonymous 64 had any affiliation with the international hacking group.

Taiwan's Mainland Affairs Council had no immediate comment.

Reuters was not immediately able to verify where the group was based or whether they had actually carried out the hacking attacks they were accused of.

In the blog post published on its official WeChat account, the most popular social media platform in China, the national security ministry said its investigation into the group had found many of the websites Anonymous 64 claimed to have accessed were fake or had little no traffic, and that its posts showing it having infiltrated numerous university and media websites had been photoshopped.

The security ministry published screenshots of the group's X account with heavily redacted text. It also said it had opened a case against three members of Taiwan's cyber warfare wing.

"We advocate that netizens should not believe in or spread rumours and should promptly report cyberattacks or cases of anti-propaganda activity to the national security authorities," the blog post said.