The WikiLeaks founder, Julian Assange, is tonight facing growing legal problems around the world, with the US announcing that it was investigating whether he had violated its espionage laws.

Assange's details were also added to Interpol's worldwide wanted list. Dated 30 November, the entry reads: "sex crimes" and says the warrant has been issued by the international public prosecution office in Gothenburg, Sweden. "If you have any information contact your national or local police." It reads: "Wanted: Assange, Julian Paul," and gives his birthplace as Townsville, Australia.

Friends said earlier that Assange was in a buoyant mood, however, despite the palpable fury emanating from Washington over the decision by WikiLeaks to start publishing more than a quarter of a million mainly classified US cables. He was said to be at a secret location somewhere outside London, along with fellow hackers and WikiLeaks enthusiasts.

In contrast to previous WikiLeaks releases, Assange has, on this occasion, kept a relatively low profile. His attempt to give an interview to Sky News via Skype was thwarted today by a faulty internet connection.

Assange's reluctance to emerge in public is understandable. It comes amid a rapid narrowing of his options. Several countries are currently either taking or actively considering aggressive legal moves against him. This lengthening list includes Sweden, Australia and now the US but so far as can be made out, not Britain.

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