STOCKHOLM/LONDON (Reuters) - Swedish police said on Thursday that technical problems hindering the arrest of Julian Assange, the founder of whistleblowing website WikiLeaks, had been overcome, and a British newspaper said he was in Britain.

Julian Assange, founder of WikiLeaks, holds a news conference at the Geneva Press Club in Geneva, November 4, 2010. REUTERS/Valentin Flauraud

A Swedish court upheld an arrest order for the 39-year-old Australian for alleged sexual crimes, refusing to let him appeal a lower court’s ruling. He denies the allegations.

A spokesman for WikiLeaks said Assange had received assassination threats and had to remain out of the public eye.

The Swedish legal case against Assange has rumbled on since September, while WikiLeaks has leaked a mass of material which has angered the United States and embarrassed some of its allies.

The latest leak was this week’s trove of U.S. diplomatic cables, some of which are embarrassing and show the thinking behind Washington’s international relations.

The Independent newspaper said Assange had arrived in Britain in October, and had given police his contact details. It cited police sources who said they knew where Assange was staying. He was believed to be in southeast England, it said.

WikiLeaks spokesman Kristinn Hrafnsson, speaking at an event in London on Wednesday night, said Assange was working on the project at a secret location.

“When you have people calling for his assassination, it is best to keep a low profile. This is inciting violence. And apparently it is unlawful in some countries,” he said.

TECHNICAL PROBLEMS HINDER ARREST

In Sweden, Assange’s efforts to have an arrest order quashed met defeat when the High Court declined to hear the case.

“The High Court has not granted a leave to appeal, so the Svea Court of Appeals ruling still stands,” High Court official Kerstin Norman told Reuters. The Svea court of appeals is one of six courts of appeal and covers the Stockholm area.

The Independent, citing unnamed sources, said Britain’s Serious Organised Crime Agency (Soca) needed clarification about the European Arrest Warrant issued by Swedish prosecutors before British police could arrest Assange.

The Metropolitan Police and Soca declined to comment when contacted by Reuters.

Tommy Kangasvieri, head of the international unit at the Swedish National Police force, said the problem over the arrest warrant had been solved.

“We have sorted this out and it will be completed during the day,” he said, adding that Swedish police had not received any official word that Assange was in Britain.

Swedish Prosecution Office spokeswoman Helena Ekstrand said the office had received no information on Assange’s location. “...the arrest warrant still stands and we are looking for Julian Assange,” she said.

Neither the British nor Swedish lawyer of Assange was available for comment.

The international police agency Interpol this week issued a “red notice” to assist in the arrest of Assange, the Independent said.

U.S. State Department spokesman P.J. Crowley, interviewed by BBC Radio 4, said Assange had failed to cooperate with a U.S. investigation into the leak.

“We’ve made clear in an exchange this weekend with Mr Assange the fact that he is in possession of classified material of the United States government, it’s stolen property and we have asked him to return it. He has declined to do that and we would investigate the implications of this.”