Sweden's prosecution authority said it had dropped its investigation into WikiLeaks founder Julian Assange over a 2010 rape allegation, even though prosecutors found the plaintiff's claim "credible".

"My assessment is that all investigative measures that can be taken have been taken. But... the evidence is not strong enough to file an indictment," deputy director of public prosecutions Eva-Marie Persson told reporters.

The 48 year-old Australian citizen has repeatedly denied the allegation against him, made in 2010.

Last month Mr Assange appeared in a British court ahead of an extradition hearing.

He is fighting a bid by the United States to extradite him on charges filed under the US Espionage Act.

Read More: Julian Assange: The world's most-wanted whistleblower

His next case management hearing will take place on 19 December, before a full extradition hearing in February. He could be sentenced to up to 175 years in a US prison if convicted on all charges.

He is being held at the high-security Belmarsh prison in southeast London.

Mr Assange used WikiLeaks to publish classified military and diplomatic files in 2010 about US bombing campaigns in Afghanistan and Iraq that proved highly embarrassing to the US government.

He has been making periodic appearances by video-link at administrative hearings as he tries to prove that he is no longer a flight risk and can be set free on bail due to poor health.

He recently served his term for violating his bail terms, when he sought asylum in the Ecuadorian embassy in London in 2012, but is still in custody while his extradition case is ongoing.