A Swedish court has upheld an arrest warrant against WikiLeaks founder Julian Assange for alleged sexual assault.

The decision is a setback for the 43-year-old Australian who has been holed up in the Ecuadoran embassy in London for the past two years trying to avoid extradition.

The Stockholm District Court reviewed the arrest warrant, which was issued in late 2010, for incidents of rape and sexual molestation that allegedly took place that year, claims Mr Assange denies.

Mr Assange sought refuge in Ecuador's embassy in Britain in June 2012 after having exhausted all legal options in the British courts to avoid being extradited to Sweden.

He has said he fears that being sent to Sweden would be a pretext for transferring him to the United States, where WikiLeaks sparked uproar with its publication of thousands of secret documents.

WikiLeaks repeatedly drove the global news agenda with revelations of the behind-the-scenes activities of governments around the world.

From confidential assessments by US diplomats of Chinese leaders to revised body counts in Iraq, the WikiLeaks documents provided the public with an unprecedented look under the hood of international politics.

Mr Assange's legal team had argued that Swedish prosecutors have dragged out the case unreasonably long by not interviewing him at the embassy.