Lawyers for Julian Assange said they would appeal after a Stockholm judge rejected their challenge to the warrant for his arrest, meaning that the WikiLeaks founder is expected to remain in the Ecuador embassy in London.

"The court believes there is probable cause for the crimes of which he is accused," judge Lena Egelin said in a statement to the court.

"He has chosen himself to go into the embassy and ... the court does not believe that the deprivation of his liberty is such as to be disproportionate" to the allegations, she said.

No charges have been brought against Assange in Sweden but he is wanted for questioning by police over allegations of sexual molestation and rape involving two women he met during a visit to the country in 2010. Prosecutors have declined to question him in London.

Assange sought refuge in Ecuador's embassy in Britain in June 2012 after having exhausted all legal options in British courts to avoid being extradited to Sweden. This was the first official legal debate in the case since that time.

"We are confident and have strong legal arguments to get the decision overruled in the Court of Appeal," Assange lawyer Tholmas Olsson told the Guardian, adding that the judge's statement was formal and gave no indication of the reasoning behind it.

"It took two hours today for the judge to rule, so it must have been a difficult decision."