Anna Ekberg, from the Swedish foreign ministry's press service, wrote to TT that the UN's Working Group on Arbitrary Detention "has judged that Assange is arbitrarily detained against international committments. The foreign ministry / government states that the working group made a different judgment than Swedish authorities."
Assange had said that he would leave the Ecuadorian embassy in London, where he has been holed up since 2012 to avoid extradition to Sweden, and accept arrest by the British authorities if the UN panel ruled against him.
In 2014, the Australian activist had complained to the panel that he was being "arbitrarily detained", since he could not leave without being arrested, according to the BBC.
The legal experts of the UN panel have gathered evidence from Sweden and the United Kingdom, but their decision has no legal effects on British or Swedish authorities.
According to the BBC, a warrant for his arrest remains in place in Britain and the UK Foreign Office argues it still has the obligation to extradite Assange.
Wikileaks was also cautious about the early reports, writing on its Twitter account: "We are waiting official confirmation".
Per E Samuelsson, Assange’s Swedish lawyer, told The Guardian, “If he is regarded detained I take it for granted that Marianne Ny and Swedish authorities will respect that decision and instantly cancel the decision to keep Mr Assange in custody."
Speaking with Radio Sweden, Samuelsson said they would argue Assange's three years at the Ecuadorian Embassy would count as time served if he had been convicted by a Swedish court.
"He has served more than his time if he would have been convicted in Swedish court"
Samuelsson said that if the UN rules in their favor it would not be binding and so the ball would be in Sweden's court.
"It's the Swedish authorities who must obey the UN report," he said. "I think it has a very strong impact. It's common practice that the states do follow the recommendations from the UN pannel. And further on, they have interpreted the convention on human rights, which is legally binding. It's a law in Sweden. So if they go against that decision, it would in principle be to go against Swedish law."
But a press release on the web page of the Swedish Prosecution Authority says that the "the opinion of the panel has no formal significance in the ongoing investigation according to Swedish law."
Sweden issued an arrest warrant for Assange in 2010, following allegations from two women in Sweden, one who claimed rape and another who alleged sexual assault.
The statute of limitations on the sexual molestation and unlawful coercion charges have already run out, but the rape case is still active.