LONDON — WikiLeaks founder Julian Assange said on Friday that there were some references to UFOs in "yet-to-be-published" confidential files obtained from the U.S. government.

In an online chat hosted by the U.K.'s Guardian newspaper, he also said that no one has been harmed by his organization's release of troves of secret documents.

"WikiLeaks has a four-year publishing history. During that time there has been no credible allegation, even by organizations like the Pentagon, that even a single person has come to harm as a result of our activities," Assange said in response to a reader's question. "This is despite much-attempted manipulation and spin trying to lead people to a counter-factual conclusion. We do not expect any change in this regard."

Assange said he and colleagues were aware of death threats following the publication of  diplomatic cables on their website.

"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 superpower," Assange was quoted as saying.

Answering questions online, Assange also said that anyone making threats against his life should be charged with incitement to murder.

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Asked if he has ever been forwarded documents dealing with UFOs or extraterrestrials, Assange responded, "Many weirdos e-mail 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. 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.

"However, it is worth noting that in yet-to-be-published parts of the Cablegate archive, there are indeed references to UFOs."

Britain's Guardian is one of a number of newspapers around the world with early access to diplomatic cables seen by WikiLeaks.

The whereabouts of Assange, a 39-year-old Australian, are unknown, but some reports have said he is believed to be in southern England.

Swedish authorities said on Friday that information missing from a European arrest warrant they had issued against Assange for alleged sex crimes had been handed to British authorities.

"We sent it. They asked for complementary information and now they have it," Swedish Prosecution Authority spokeswoman Karin Rosander said.

Bjorn Hurtig, Assange's attorney in Sweden, told Dutch TV that the WikiliLeaks founder would fight extradition if arrested.

Hurtig repeated Assange's denials of a sexual crime in Sweden and said any evidence against him was "very very weak."

"One woman says it's rape another woman says its a sexual offense," Hurtig said. "I will not say if he says he has had sex with them. I will tell you he denies rape he denies sexual offenses he denies having committed any sort of crime against these women or against any other person."