London (AFP) - WikiLeaks founder Julian Assange started his fifth year camped out in the Ecuadoran embassy in London on Sunday, an occasion marked by his supporters with events celebrating whistleblowers.

Supporters held talks in European cities including Athens, Berlin, Brussels and Madrid, which Assange addressed through a live video stream from inside the embassy.

"I am normally very isolated here at the embassy," Assange said, noting it was strange to address so many people.

"It's quite incredible to see this extent of support."

The 44-year-old is wanted for questioning over a 2010 rape allegation in Sweden but has been inside Ecuador's UK mission for four full years in a bid to avoid extradition.

The anti-secrecy campaigner, who denies the allegation, walked into the embassy of his own free will on June 18, 2012, with Britain on the brink of sending him to Stockholm, and has not left since.

His lawyers say he is angry that Swedish prosecutors are still maintaining the European arrest warrant against him.

The Australian former computer hacker fears that from Sweden he could be extradited to the United States over WikiLeaks' release of 500,000 secret military files, and could face a long prison sentence there.

Figures including musician Brian Eno, fashion designer Vivienne Westwood, and academic Noam Chomsky sent video messages of support that were screened at the events.

"Julian Assange's crime is to violate the fundamental principles of government, to lift the veil of secrecy that protects power from scrutiny, keeps it from evaporating," Chomsky said in a video message.

"We should all thank Julian for his courage and integrity in providing us with this precious gift at great cost to himself, much to our shame."

- 'Political persecution' -

In Madrid, news site eldiario.es organised a panel discussion with judge Baltasar Garzon, who described the WikiLeaks founder as a victim of "political persecution".

An event in Brussels event was addressed by the former Greek finance minister Yanis Varoufakis, who said the treatment of Assange was aimed at "killing off... the chance of democracy," the economist said.

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French composer Jean Michel Jarre and British left-wing filmmaker Ken Loach both called on Assange to be freed.

"He should be able to leave his place of safety without fear of deportation or being handed over to those who intend him harm," Loach said.

A hero to supporters and a dangerous egocentric to detractors, Assange founded WikiLeaks in 2006 and has been portrayed in two movies in recent years.

Assange has compared living inside the embassy -- which has no garden but is in London's plush Knightsbridge district, near Harrods department store -- to life on a space station.

His 15 feet by 13 feet (4.6 by 4 metre) room is divided into an office and a living area. He has a treadmill, shower, microwave and sun lamp and spends most of his day at his computer.

He got a cat in May to give him some company.

- Assange backs Brexit -

Last month a Stockholm district court maintained a European arrest warrant against Assange, rejecting his lawyers' request to have it lifted.

"The court considers that Julian Assange is still suspected of rape... and that there is still a risk that he will abscond or evade justice," it said in a statement.

Assange will appeal the ruling, one of his Swedish lawyers, Per Samuelsson, told AFP.

"He is not surprised but very critical and angry," he said.

Assange's lawyers requested the lifting of the warrant after the UN Working Group on Arbitrary Detention issued a non-binding legal opinion on February 5 saying his confinement in the Ecuadoran embassy amounted to arbitrary detention by Sweden and Britain.

London and Stockholm have angrily disputed the group's findings.

The alleged crime dates back to 2010 and the statute of limitations expires in 2020.

Assange is calling for Britain to leave the European Union in Thursday's closely-watched referendum on its membership of the bloc.

He alleges that British authorities "repeatedly use the EU as political cover for its own decision-making", highlighting the European arrest warrant.