WikiLeaks founder Julian Assange claims he has "insurance" files on Australian media mogul Rupert Murdoch that will be released if "something happens" to him.
Mr Assange has enraged the United States with his website's release of leaked diplomatic cables, and the Australian's defence team believe efforts are under way to send him to the US where they claim he could face the death penalty.
In an interview Britain's New Statesman magazine, conducted by veteran journalist John Pilger who is a prominent supporter of the Australian hacker, Mr Assange said WikiLeaks had "504 US embassy cables on one broadcasting organisation" and "cables on Murdoch and News Corp", without going into more detail on what they contained.
"If something happens to me or to WikiLeaks, 'insurance' files will be released," Mr Assange was cited as saying.
Lawyers for Mr Assange, who is on bail in England as he fights attempts to extradite him to Sweden for questioning on allegations of sexual assault, have argued that if Mr Assange was extradited to Sweden there was a "real risk" he will face extradition or illegal rendition to the United States, where he could be detained at Guantanamo Bay or elsewhere and subject to the death penalty.
Mr Assange insists that attempts to extradite him to Sweden are politically motivated and linked to WikiLeaks's activities.
He has been living at the country estate of a friend in eastern England since being released on bail on December 16, nine days after his arrest by British police on a Swedish warrant.
A British judge ruled on Tuesday that Sweden's bid to have him extradited would be heard in full on February 7-8.
WikiLeaks has also released classified documents about the wars in Iraq and Afghanistan.
US soldier Bradley Manning is in military custody in the United States awaiting trial for having allegedly obtained and leaked the cables.
A US court has reportedly subpoenaed the Twitter accounts of four WikiLeaks supporters as part of a criminal investigation into the leaks.
Mr Assange told New Statesman attempts by the US to indict him should worry the mainstream press as well.
"I think what's emerging in the mainstream media is the awareness that if I can be indicted, other journalists can, too," Mr Assange said in the interview published on Thursday.
"Even The New York Times is worried. This used not to be the case. If a whistleblower was prosecuted, publishers and reporters were protected by the First Amendment, which journalists took for granted. That's being lost."
In the interview, Mr Assange also blasted China as the "technological enemy" of his whistleblower website because of its aggressive internet censorship, in comments published Thursday.
But China, with its vast internet censorship system known as the "Great Firewall", was the site's most feared foe in cyberspace, the 39-year-old told New Statesman.
"China is the worst offender" when it comes to censorship, he said.
"China has aggressive and sophisticated interception technology that places itself between every reader inside China and every information source outside China.
"We've been fighting a running battle to make sure we can get information through, and there are now all sorts of ways Chinese readers can get on to our site."