Sweden's foreign ministry says a UN advisory panel has concluded that Julian Assange, WikiLeaks founder, has been a victim of "arbitrary" detention at the Ecuadorean embassy in London where he sought refuge in 2012.

Sweden has seen the report, to be published on Friday, and the Geneva-based UN panel concluded that it "was an arbitrary detention".

"It is a different assessment than what the Swedish authorities have made," Katarina Byrenius Roslund, foreign ministry spokesman, said, declining further comment.

The Working Group on Arbitrary Detention has not revealed its decision, saying it would remain confidential until Friday, said Christophe Peschoux of the UN human rights office in Geneva.

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A finding in Assange's favour would not be binding on authorities in Sweden and Britain, which seek to arrest and question him, but it would represent a public-relations victory for the 44-year-old Australian.

It could increase pressure on Swedish prosecutors to drop their bid to question Assange about allegations of sexual misconduct, and on British officials to alter plans to arrest Assange for jumping bail.

Swedish officials would not comment on their plans on Thursday, and British police said plans to arrest Assange if he leaves the Ecuadorean embassy in London remain unchanged.

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However, Geoffrey Robertson QC, a former UN appeals judge and international lawyer, told Al Jazeera that a UN ruling would be "binding in honour".

"It is a very important tribunal and Britain and Sweden are on a bound to abide by its decision," he said.

Assange has been in the embassy for more than three years. His organisation WikiLeaks was responsible for publishing millions of documents considered classified by the US government.

Assange's supporters have planned a news conference in London for that day to discuss his plans.

Assange has said via Twitter that he expects to have his confiscated passport returned in light of the UN report and to be free to travel.

He is expected at the news conference, either in person or - more likely - in a video link from his safe haven at the embassy.

One of his lawyers told the Associated Press news agency on Thursday he may travel to Ecuador, which has given him political asylum, if he recovers his passport and his liberty.

Source: Al Jazeera and agencies