WikiLeaks founder Julian Assange appeared in court in London on Monday to hear whether he should be extradited to the United States to face espionage charges.

Assange raised his grip for his supporters, and appeared with a blue jacket, and was shaved, contrary to the image that appeared after leaving a long beard from the Embassy of Ecuador to which he had taken refuge.

Assange, 48, faces 18 charges in the United States, including hacking and conspiracy to hack government computers, violating espionage laws and could serve jail terms if convicted.

Australian-born Assange made world headlines in early 2010, when WikiLeaks released a secret US military video of a 2007 Apache attack in Baghdad that killed more than a dozen people, including two Reuters journalists.

He admired Assange as a hero for revealing what they described as the abuse of power by modern nations and for his defense of freedom of expression.

His opponents paint a dangerous portrait of him, complicit in Russian efforts to undermine security in the West and the United States, and doubt he is a journalist.

WikiLeaks has angered Washington by publishing hundreds of thousands of secret US diplomatic cables, which have uncovered US assessments involving criticism of world leaders, from Russian President Vladimir Putin to members of the Saudi royal family.

In 2012, Assange sought refuge in the Ecuadorian embassy in London to avoid being extradited to Sweden, where he was charged with sex offenses he denies, saying he believes he will eventually be extradited to the United States.

He was taken from the embassy in April after spending seven years, and was sentenced to 50 weeks' imprisonment for not paying bail, and continued his detention, but remained imprisoned pending a decision on his extradition.