WikiLeaks founder Julian Assange walked free on Wednesday after he pleaded guilty to a single felony charge for publishing military secrets in a US court. Photo: Internet Source

Asked by the judge whether he would plead guilty or not guilty, Assange replied, "Guilty to the information."

The plea was part of a deal with US persecutors that concluded a drawn-out legal saga that raised divisive questions about press freedom and national security.

"With this pronouncement, it appears that you will be able to walk out of this courtroom a free man," the judge said.

The US banned Assange from entering the country without prior approval as part of his plea deal.

"Pursuant to the plea agreement, Assange is prohibited from returning to the United States without permission," the Department of Justice said in a statement.

Assange's legal team hailed the news as he boarded a plane to Australia.

"Today is a historic day. It brings to an end 14 years of legal battles," lawyer Jen Robinson told reporters outside court.

"It also brings to an end a case which has been recognized as the greatest threat to the First Amendment in the 21st century."

Another lawyer, Barry Pollack, said that "the prosecution of Julian Assange is unprecedented in the 100 years of the Espionage Act, it has never been used by the United States to pursue a publisher, a journalist, like Mr Assange."

Australian Prime Minister Anthony Albanese also said Wednesday's plea hearing was a "welcome development."

"Given those proceedings that are happening literally in real time, it isn't appropriate to provide further commentary," Albanese told reporters.