Websites owned by Rupert Murdoch's News International were down Tuesday after the Lulz Security hacker group replaced The Sun's online version with a fake story pronouncing the mogul's death.

The British tabloid quickly took down reports that the 80-year-old had been found dead in his garden after ingesting palladium but visitors to the site were redirected to LulzSec's Twitter feed, which celebrated the high-profile attack.

News International, Murdoch's British newspaper arm, is believed to have swiftly pulled all of its websites as a precautionary measure.

"We have owned Sun/News of the World - that story is simply phase 1 - expect the lulz to flow in coming days," a message from the group warned.

Another message taunted "We have joy we have fun, we have messed up Murdoch's Sun"

A News International spokeswoman said the company was "aware" of the attack.

The hacker collective said it was "sitting on their (the Sun's) emails" and was prepared to publicise them on Tuesday.

Lulz has been in the spotlight after taking credit for cyberattacks on high-profile companies including Sony and Nintendo.

News International has been under fire over accusations that its now defunct News of the World tabloid hacked into the phone of murdered schoolgirl Milly Dowler.