Affiliates of the international hacking network Anonymous have questioned the authenticity of a post purported to have come from the group on the neo-Nazi website the Daily Stormer.
The post on the website's homepage was headlined: "End of hate: Anonymous now in control of Daily Stormer."
The Daily Stormer was founded and is edited by US-born Andrew Anglin, who endorsed Donald Trump for president.
On Sunday Anglin published an article on the site criticizing Heather Heyer, who was killed during violence at a white supremacist march in Charlottesville, Virginia, on Saturday.
The web-hosting company GoDaddy said on Sunday it had given the Daily Stormer 24 hours to move its domain to another provider, after the article denigrating Heyer was published.
Your Anon News, one of the biggest Anonymous-linked Twitter accounts, said on Monday that it did not think the hack had been perpetrated by an established member.
"We have no confirmation that ‘Anonymous' is involved yet," it wrote on Twitter. Furthermore, the account suggested the post may have been a Daily Stormer stunt.
The post in the name of Anonymous claims that the website will be shut down within 24 hours, but this was almost inevitable considering GoDaddy''s withdrawal of support.
"Looks more like a [Daily Stormer] stunt," the Your Anon News account said. "Wonder if they are having issues finding a new host."
Heyer, a legal assistant who had championed civil rights issues, was killed on Saturday when a plowed into a crowd of protesters who had assembled to challenge a white supremacist rally in Charlottesville.
The post on Monday said Anonymous had taken over the site in Heyer's name, stating she was a "victim of white supremacist terrorism."
"For too long the Daily Stormer and Andrew Anglin have spewed their putrid hate on this site," it said. "This evil cannot be allowed to stand. It took a united force of elite hackers from around the world to breach the systems and the firewall.
"The events of Charlottesville alerted us to the need for immediate action. We want you Nazis to know: your time is short."
Anonymous is a hacking collective that grew out of the internet forum 4Chan in the late 2000s. It has become well known for a series of high-profile cyber-attacks on political, religious and corporate organizations, including Islamic State, the Westboro Baptist church, PayPal, MasterCard, Visa and Sony.
The group has described itself as having "a very loose and decentralized command structure". In public, Anonymous members or supporters often wear Guy Fawkes masks in the style portrayed in the graphic novel and film V for Vendetta.
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