Swedish authorities say they have issued an arrest warrant for Wikileaks founder Julian Assange, on accusations of rape and molestation.
The warrant was issued late on Friday, said Karin Rosander, communications head at Sweden's prosecutors' office.
Swedish police have been trying to contact Mr Assange, but have not yet been able to, she told the BBC.
Wikileaks, criticised for leaking Afghan war documents, quoted him saying the allegations were "without basis".
The message, which appeared on Twitter and was attributed directly to Mr Assange, said the appearance of the allegations "at this moment is deeply disturbing".
In a series of other messages posted on the Wikileaks Twitter feed, the whistle-blowing website said: "No-one here has been contacted by Swedish police", and that it had been warned to expect "dirty tricks".
More documents due
Last month, Wikileaks published more than 75,000 secret US military documents on the war in Afghanistan.
US authorities criticised the leak, saying it could put the lives of coalition soldiers and Afghans, especially informers, at risk.
Mr Assange has said that Wikileaks is intending to release a further 15,000 documents in the coming weeks.
Ms Rosander said there were two separate allegations against Mr Assange, one of rape and the other of molestation.
She gave no details of the accusations. She said that as far as she knew they related to alleged incidents that took place in Sweden.
Media reports say Mr Assange was in Sweden last week to talk about his work and defend the decision by Wikileaks to publish the Afghan war logs.
The allegations were first reported in the Swedish newspaper Expressen.