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A Swedish court has upheld the arrest warrant for Julian Assange to be extradited to Sweden over sexual assault allegations.

The ruling leaves the WikiLeaks founder no closer to leaving the tiny Ecuadorian embassy in London that's been his home for more than four years.

Swedish investigators in 2012 issued a European arrest warrant, which required British police to detain Assange and extradite him. Fearing that Sweden could send him to the US to face investigation over US diplomatic cables and other documents published on WikiLeaks, Assange took refuge in Ecuador's embassy. He's been there ever since, confined to a converted office with a bed, shower, treadmill and sunlamp.

On Friday, Sweden's Court of Appeal issued the decision on Assange's appeal against extradition. The ruling upholds the warrant, meaning there is no change in his situation. "The Court of Appeal shares the assessment of the District Court," it states, "that there is still a risk that Julian Assange will flee or otherwise evade legal proceedings or a penalty."

The ruling continues, "Ultimately this is a question of weighing the public interest of the suspected offence being investigated in a secure way against the right of the individual not to have their freedom of movement."

It concludes that the risk Assange could flee, combined with the public interest of the case, outweigh the detriment to Assange.

A statement posted on the WikiLeaks Twitter feed railed at Sweden's government and announced that Assange's legal team intends to appeal the decision.

"Sadly, Sweden has a long history of compromising its rule of law where the perceived interests of the United States are concerned," it reads in part. "Mr. Assange ... remains confident that his indefinite and unlawful detention will cease and that those responsible will be brought to justice."

WikiLeaks and Assange's legal team did not immediately respond to a request for further comment.

The court's statement notes that the appeal relates to the extradition and not to the original accusations, alleged to have occurred in 2010: "It should be specifically pointed out that the question of guilt has not been decided."

Following Friday's ruling, Assange is unlikely to leave the embassy anytime soon. British police could arrest him over violation of his bail conditions, and for now he's still under investigation by Swedish prosecutors. Having previously refused to interview Assange at the embassy, Swedish authorities will visit London and question him through an Ecuadorian prosecutor on 17 October.

Assange claimed a moral victory in February when a UN panel ruled he'd been "arbitrarily detained" during his time in the cramped embassy building. The UN Working Group on Arbitrary Detention said that Assange, having endured "deprivation of liberty" without due legal process, was entitled to both freedom and to compensation for his time in exile.

However, the Swedish Court of Appeal maintains that it is not bound by the conclusions of the UN body.

Editors' note, 16 September: This story was first published on 15 September and has been updated with details of the Swedish court's ruling.