The 39 year-old Australian, who is wanted by Interpol over a charge of rape and sexual assault in Sweden, said there were some references to extraterrestrial life in yet-to-be-published confidential files obtained from the American government.
He did not disclose what information was contained in the diplomatic memos obtained by the whistleblowing website. It also remains unclear when they will be published.
Mr Assange said his website, under considerable strain in recent days over its “Cablegate” series of leaks, received emails from “weirdos” claiming to have seen UFOs.
“Many weirdos email us about UFOs or how they discovered that they were the anti-christ whilst talking with their ex-wife at a garden party over a pot-plant,” he wrote when asked if any of the documents he had received referred to extraterrestrial life.
“However, as yet they have not satisfied two of our publishing rules. 1) that the documents not be self-authored; 2) that they be original.”
“It is worth noting that in yet-to-be-published parts of the cablegate archive there are indeed references to UFOs.”
Last year there were almost 400 reported sightings to the Ministry of Defence of UFOs throughout Britain – a figure that had tripled from the previous year.
The so-called “X Files” reported to the MoD’s UFO desk, which has since been closed, was the busiest year on record.
Some websites later speculated that the cables could offer answers to claims from US military pilots that aliens have landed, infiltrated British nuclear missile sites and deactivated the weapons.
Mr Assange’s comments were made during a webchat with The Guardian, during which he confirmed his team were taking security precautions due to “threats against our lives”.
Mr Assange is under intense scrutiny worldwide after his website began releasing a selection of more than 250,000 classified US diplomatic cables passed to the whistle-blowing website.
Sarah Palin, the former Republican vice-presidential candidate, has called for him to be hunted down like the al-Qaeda leadership while other members of her party have directly called for a capital sentence against WikiLeaks personnel.
“The threats against our lives are a matter of public record. However, we are taking the appropriate precautions to the degree that we are able when dealing with a super power,” Assange wrote in response to a reader’s question.
A Canadian pundit called earlier this week for him to be assassinated for leaking US diplomatic cables, while former Republican presidential hopeful Mike Huckabee said those responsible for the leaks should face execution.
The Swedish authorities are also seeking Mr Assange over a charge of rape and sexual assault. Interpol has issued an international warrant for his arrest.
British police requested more information about the penalties Mr Assange could face if convicted, according to a statement on the Swedish Prosecution Authority’s website.
It is understood that this has now been provided, although the Metropolitan Police refused to discuss whether officers from its extradition unit were preparing to arrest Mr Assange.