Founder of WikiLeaks Julian Assange said at a London court on Tuesday that he will fight against extraditing him to Sweden over sexual assault claims.

Assange was refused bail after being charged with four sexual offences and will appear in court on Dec. 14. He told City of Westminster magistrates that he would refuse to return to Sweden.

Officers from Scotland Yard detained the 39-year-old Australian at about 0930 GMT after he voluntarily went to a police station in central London. Britain has received a European arrest warrant from Sweden on Monday.

Two women in Sweden accused Assange of sexually attacking them when he visited the country in August, but Assange denied the claims.

His lawyer Mark Stephens has said his client wants to find out what allegations he faces so he can clear his name.

Over the last week, his website has revealed hundreds of secret American diplomatic documents. British Foreign Secretary William Hague said publishing details of sensitive sites, including some in Britain, could make them become the targets attacked by terrorists.

On Monday, Prime Minister David Cameron’s national security adviser also ordered all government departments to provide assurance about the quality of IT security.