Sweden's Supreme Court has said that it will hear an appeal by WikiLeaks founder Julian Assange to overturn the arrest warrant against him issued by prosecutors who want to question him over allegations of sexual assault.

The 43-year-old Australian has been holed up inside Ecuador's London embassy since June 2012 to avoid extradition to Sweden, where he is wanted for questioning over allegations of sexual assault against two women in 2010. He denies the accusations.

Prosecutors first insisted Assange should come to Sweden for questioning, but in a U-turn in March 2015 agreed to conduct the interview in London.

Assange has said he fears that if Britain extradited him to Sweden he would then be extradited on to the US where he could be tried for one of the largest leaks of classified information in the country's history.

Even if Sweden drops the investigation, he faces arrest by British police for jumping bail granted while the British courts considered the European arrest warrant issued by Sweden.

"The Supreme Court grants leave to appeal in the matter regarding the arrest," the court said in statement which provided no date at which the appeal would be heard.

Assange's Swedish lawyers were not immediately available for comment.