Rupert Murdoch's British newspaper group told staff to change their passwords and tighten security, sources said on Tuesday, after hackers attacked the website of his tabloid The Sun.
Hackers on Monday redirected The Sun's online readers to a fake page which reported Murdoch had been found dead in his garden.
Members of the hacking group LulzSec, who recently announced they had disbanded, took responsibility for the attack in messages posted via the social networking site Twitter and said they was preparing more online assaults.
They also posted jokes and abusive messages about Murdoch and his media empire, both caught up in a phone-hacking scandal that has rocked Britain's establishment right up to Prime Minister David Cameron.
"Within 20 minutes, pages are overloading, things are crashing! We are working our way through the cracks right now. Stay tuned for more," LulzSec said in one Twitter message.
"We have joy, we have fun. We have messed up Murdoch's Sun," another of its messages said.
Two sources inside Murdoch's print headquarters in London said staff at Murdoch's newspapers, including the Sunday Times, had been told to change their passwords.
A spokesperson for News International, parent company of The Sun, The Times and The Sunday Times, declined to comment on the security measures.
"We are aware of the hacking attempt on the sun.co.uk last night and our sites are now back up. We do not have any further comment to add at this time."
