WikiLeaks founder Julian Assange has lost an appeal against a Swedish warrant for his arrest to be questioned over alleged sex crimes.

"The Court of Appeal refuses Julian Assange's claim that the detention order of the city court be set aside," the ruling announced on Thursday.

The 43-year-old Australian, who has been holed up in the Ecuador embassy in London since 2012 to avoid extradition to Sweden was "detained in absence" by a district court in 2010, and an earlier application to drop the arrest warrant was dismissed in July.

Swedish prosecutors want to question Mr Assange about accusations of rape and sexual molestation brought against him by two women in their 30s when he visited the country in 2010. He denies the claims.

A European arrest warrant has also been issued to support the Swedish move.

Mr Assange had called on Swedish prosecutors to travel to London to question him or, alternatively, to do so by video link, but the appeal court rejected the demand.

The court agreed said that "interviews must take place here in Sweden in view of the nature of the crimes and the investigation and the fact that a possible trial requires him to be in Sweden", dismissing Mr Assange's claim that he is effectively under house arrest.

"The fact is that Julian Assange can leave the embassy if he so wishes," the ruling said.

This fact means that the restriction of his freedom cannot be equated with a deprivation of liberty."

Mr Assange said he feared that if Britain extradited him to Sweden, he would then be extradited to the United States where he could be tried for one of the largest information leaks in US history.

ABC/AFP