The United States Justice Department has charged founder of Wikileaks Julian Assange with new espionage charges.

The US alleges that classified government documents were published by Assange to his Wikileaks website that included the names of confidential military sources whose safety was jeopardised.

The latest 17 charges go much further than the first indictment that became public last month when Assange was dragged from the Ecuadorian embassy in London by UK police. He was initially accused of conspiring with Chelsea Manning, a former US intelligence analyst, to crack a password on a Department of Defence computer system.

The indictment alleges that Assange “risked serious harm” to the United States with his actions.

The case has caused many to express concern over whistle-blower protection and media freedom, with the US Justice Department saying that Assange had gone beyond the protection the First Amendment.

Wikileaks says that its role is to publish “censored or otherwise restricted official materials involving war, spying and corruption”.

However, assistant Attorney-General John Demers says that “Assange is no journalist” and that “no responsible actor, journalist or otherwise, would purposely publish the names of individuals he or she knew to be confidential sources, exposing them to the gravest of dangers.”

The Justice Department claims that the most harm was caused by the leaking of documents containing the names of informants who aided forces in Afghanistan and Iraq.

He is currently serving a 50-week term in London for breaching bail conditions after he sought initially refuge in the Ecuadorian embassy. The US is now seeking his extradition.

Manning is now being held in a jail in Northern Virginia for refusing to testify against Assange.