A senior Swedish judge has said that the sex-crime allegations against Wikileaks founder Julian Assange are "a mess", and praised him for leaking classified US documents.

Speaking on Wednesday at the University of Adelaide in Australia, Stefan Lindskog, chairman of the Supreme Court of Sweden, also listed legal obstacles to extraditing the 41-year-old Australian to the United States to face prosecution for exposing thousands of classified documents.

Lindskog was critical of the Swedish criminal investigation, and suggested that Sweden's extradition treaty with the United States would not apply to Assange.

"I think it is a mess,'' said Lindskog, referring to the Swedish criminal investigation. "Basically, I think there are some misunderstandings, especially when it comes to the issue of extradition.''

"Extradition shall not be granted when alleged crimes [are] military or political in nature,'' Lindskog said.

Assange has taken asylum in the Ecuadorean Embassy in London since last June to avoid extradition to Sweden on sex crime allegations.

Criminal allegations

Assange is wanted in Sweden for questioning over criminal allegations made by two women.

However, he says the allegations are a ploy to get him to Sweden from where he would be extradited to the US.

The US Department of Justice has been investigating WikiLeaks since the website began distributing hundreds of thousands of classified US documents.

Few details of that investigation have been made public.

Assange has refused to comment on whether he had any dealings with Bradley Manning, a US soldier who admitted to leaking classified documents and video clips to Wikileaks, but called him a political prisoner.

Lindskog praised Assange's campaign of publishing the classified information through WikiLeaks.

"He'll be thought of as a person who made public some pieces of classified information to the benefit of mankind," he said.

"It should never be a crime to make known [a] crime of a state,'' he added.