Wikileaks founder Julian Assange has been sentenced to 50 weeks' jail for absconding while on bail, when he fled to the Ecuadorian embassy in London in 2012.

Key points: Julian Assange first took refuge at the Ecuadorian embassy in London in 2012

Julian Assange first took refuge at the Ecuadorian embassy in London in 2012 He was avoiding extradition to Sweden over a since-dropped sexual assault case

He was avoiding extradition to Sweden over a since-dropped sexual assault case Assange's lawyers say he will fight a US extradition attempt over allegations he conspired with Chelsea Manning to access classified databases

Assange was granted asylum by Ecuador after the UK Supreme Court upheld a ruling that he should be extradited to Sweden over a sexual assault case that has since been dropped. He has denied the allegation.

He claimed he was seeking political asylum because Sweden's international arrest warrant would see him eventually extradited to the United States.

Assange's lawyer Mark Summers told the courtroom packed with journalists and WikiLeaks supporters that his client sought refuge in the Ecuadorian embassy because "he was living with overwhelming fear of being rendered to the US".

He said Assange had a "well-founded" fear that he would be mistreated and possibly sent to the US detention camp for terrorism suspects at Guantanamo Bay.

Mr Summers read a letter from Assange apologising for his behaviour in 2012 and saying, "I did what I thought was best".

"I found myself struggling with terrifying circumstances," the letter said.

The white-haired WikiLeaks founder stood impassively with his hands clasped while his 50-week sentence was read.

The 47-year-old's supporters in the public gallery chanted "shame on you" at the judge as he was led away.

'Exceptional in seriousness'

Assange supporters shouted "shame on you" as the judge read out the verdict. ( AP: Matt Dunham )

Assange had apologised unreservedly to the court for skipping bail seven years ago and moving to the Ecuadorian embassy.

After six years holed up inside, Assange was arrested and dragged out to a waiting police van on April 11.

Ecuador's President Lenin Moreno said the country had withdrawn its offer of asylum and accused Assange of harassing embassy staff.

Kristinn Hrafnsson, editor-in-chief of WikiLeaks, and barrister Jennifer Robinson address the media in London. ( AP: Frank Augstein )

The next day, he was found guilty of breaching his bail at Westminster Magistrates' Court.

During sentencing remarks, Judge Deborah Taylor said she had taken into consideration "the seriousness of the failure to surrender, the level of culpability and the harm caused".

She called the harm "exceptional in seriousness", saying it put the offence outside the range of "even the highest category".

"By entering the embassy, you deliberately put yourself out of reach, whilst remaining in the UK," she said.

"You remained there for nearly seven years, exploiting your privileged position to flout the law and advertise internationally your disdain for the law of this country."

She said it had cost taxpayers 16 million pounds ($25.5 million) to ensure that Assange was arrested when he left the embassy.

In a press conference, Kristinn Hrafnsson, editor-in-chief of Wikileaks, said, "only two weeks short of a maximum sentence is an outrage".

Julian Assange was impassive in the court. ( Supplied: Julia Quenzler )

Assange faces extradition hearing

On Thursday, Assange will again appear in court by video link as the US attempts to extradite him.

Assange is charged with conspiring with former Army intelligence analyst Chelsea Manning to gain access to classified databases.

In 2010, WikiLeaks released hundreds of thousands of US military reports about the wars in Afghanistan and Iraq and US diplomatic communications.

The US Justice Department described it as "one of the largest compromises of classified information in the history of the United States".

Assange faces up to five years in US prison if convicted. Assange's lawyers said they would fight the extradition attempt.

"What is at stake there will be a question of life and death for Assange … and for major journalistic principles," Mr Hrafnsson told the media.

Assange's lawyer Jennifer Robinson added that the "focus of [their] energy" would now move to fight the extradition request.

Julian Assange was arrested in London in April after years in the Ecuadorian embassy. ( Reuters: Hannah McKay )

ABC/AP