Sweden's highest court decided Tuesday to allow Julian Assange to appeal a detention order against the WikiLeaks founder over allegations of sex crimes.

The Swedish Supreme Court said it has "granted leave to appeal the issue of detention." It gave no reason for the decision.

The move follows a surprise reversal by Swedish prosecutors last month of their long refusal to question Assange in London where he has been holed up in the Ecuadorean Embassy for nearly three years, fearing extradition to Sweden. It is not clear when they will travel to London to question him.

Since 2010, prosecutors have sought to interrogate Assange over allegations of rape, sexual molestation and illegal coercion made by two women after his visit to Sweden that year.  Assange denies the allegations and has not been formally indicted. He believes extradition to Sweden would merely be a first step in efforts to remove him to the U.S., where WikiLeaks infuriated officials by publishing secret documents including 250,000 State Department cables.

Former U.S. Army soldier Chelsea Manning is serving a 35-year sentence for passing those documents to WikiLeaks and the U.S. investigation into WikiLeaks is ongoing.

After failing to fight extradition through the British courts, Assange took refuge inside Ecuador's small diplomatic mission outside which British police stand guard around the clock ready to arrest him if he steps out.

Tuesday's court decision doesn't change that, although one of Assange's lawyers in Sweden, Per Samuelsson, said it was a "big success" for Assange.

"This is good for us and we've been working for this for almost a year," Samuelsson told The Associated Press, but added that the real battle, to win the appeal of the detention order, starts now.

Samuelsson, who earlier had greeted the prosecutors' decision to question Assange in London, said that even if an appeal to the Supreme Court of the detention order is successful, the investigation continues and Assange would be interrogated by prosecutors.

"He still has his political asylum to protect against extradition to the United States so he can't just leave the embassy because then we would lose his political asylum," he said.