WikiLeaks founder Julian Assange has berated the United States from the balcony of the Ecuadorian embassy where he has sought refuge from arrest, challenging President Barack Obama to end what he called a witch-hunt against his whistle-blowing website.

Speaking from within the London mission to avoid being detained by British police who want to extradite him to Sweden for questioning over rape allegations, Assange said the United States was fighting a war against outlets like WikiLeaks.

Pitching himself alongside Russian punk band Pussy Riot and the New York Times newspaper, Assange said the United States risked shunting the world into an era of journalistic oppression. He did not mention the rape allegations.

"As WikiLeaks stands under threat, so does the freedom of expression and the health of all of our societies," Assange said, dressed in a maroon tie and blue shirt, flanked by the yellow, blue and red Ecuadorian flag with dozens of British policemen lined up on the pavement below.

"I ask President Obama to do the right thing: the United States must renounce its witch-hunt against WikiLeaks," Assange said in a 10-minute speech which he ended with two thumbs up to the world's media.

Ecuadorian President Rafael Correa, a self-declared enemy of "corrupt" media and US "imperialism", granted the former computer hacker political asylum last week, deepening a diplomatic standoff with Britain and Sweden.

Asylum in Ecuador marked the latest twist in a tumultuous journey for Assange since he incensed the United States and its allies by using his WikiLeaks website to leak hundreds of thousands of secret US diplomatic and military cables in 2010, disclosures that often embarrassed Washington.

Assange, 41, took sanctuary in the embassy in June, jumping bail after exhausting appeals in British courts against extradition to Sweden, where he is wanted in Sweden for questioning regarding allegations of rape and sexual assault against two women.

He says he fears Sweden will eventually hand him over to the United States where, in his view, he would face persecution and long-term imprisonment. The United States says it is not involved in the matter.

'WITCH-HUNT'?

To allow Assange to avoid arrest by stepping outside the embassy, a balcony door on an upper floor was removed, leading up to his first public appearance since seeking refuge in the diplomatic mission.

Despite having to stomach the apparent defiance of Assange scolding the world's superpower from a balcony in its capital, Britain's Foreign Office refused comment.

Speaking behind the condor of the Ecuadorian coat of arms on the white balcony railing of the embassy, Assange thanked Correa and Ecuador's diplomats, whom he praised for standing up against oppression.

"The sun came up on a different world and a courageous Latin American nation took a stand for justice," Assange, with cropped hair indicating a recent cut, said from the balcony.

Assange's attempt to escape extradition has touched off a diplomatic tussle between Britain and Ecuador, which accused London of threatening to raid its embassy and casting the dispute as an arrogant European power treating a Latin American nation like a colony.

Assange, who praised a dozen Latin American countries which he said had rallied against Britain in the dispute, said the United States was at a turning point which could drag the rest of the world into a new oppressive era.

He said US army intelligence analyst Bradley Manning, accused of the largest leak of classified documents in US history to WikiLeaks, was a hero who should be released by the United States.

Manning faces life in prison if convicted.

"If Bradley Manning did as he is accused, he is a hero and an example to all of us and one of the world's foremost political prisoners," said Assange. "Bradley Manning must be released."

'FIGHTING SPIRIT'

More than 50 of Assange supporters, many of whom have slept on sheets of cardboard outside the building since Wednesday (Thursday, NZT), decorated barriers with messages of support for Assange and placards reading "asylum - end the witch hunt".

"They are not treating him fairly," said Chantal, 28, a French pro-WikiLeaks blogger who had travelled overnight with a friend from near Paris in the hope of seeing Assange speak.

"Great Britain has shown it doesn't respect human rights - political asylum is a right which should be respected by all countries," she said. She refused to give her surname.

There was also a large crowd of curious passersby and bemused shoppers with bags from the ritzy Harrods store nearby watching the proceedings from across the street.

"Julian Assange is in fighting spirit," Baltasar Garzon, a Spanish jurist and prominent human rights investigator who heads Assange's legal team, told reporters outside the embassy.

"He is thankful to the people of Ecuador and to President Correa for granting him asylum," said Garzon.

Britain says the dispute is about its legal obligations and that Assange should be extradited to Sweden. But Assange says he fears he will eventually be sent to the United States although Washington has so far kept its distance from the dispute.

- Reuters