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WikiLeaks founder Julian Assange has denied speculation that US intelligence leaker Edward Snowden was interrogated by Russian authorities, telling Australian media they had "behaved well".

Snowden, who is wanted by Washington on espionage charges linked to his disclosures about the secret details of US surveillance programmes, was granted asylum by Russia on August 1 after spending some five weeks at Moscow airport.

Assange, who is standing for election in Australia's upcoming national polls, said WikiLeaks personnel had been with Snowden since he left Hong Kong and arrived in Sheremetyevo airport's transit zone on June 23.

"Since Hong Kong we have had someone physically by his side the entire time," he said in an interview with Australia's Fairfax Media published online Friday.

"We have had someone with him for 54 days."

Asked whether Snowden had been interviewed by Russia's Federal Security Service (FSB) or any other Russian intelligence agency, Assange said: "No, he has not."

The FSB was reported to have been working with the US Federal Bureau of Investigation on resolving the impasse over Snowden before he was given temporary asylum, and there has been speculation they would have questioned him.

But Australian-born Assange said that personnel from his whistleblowing website WikiLeaks had been "watching the situation closely and the Russian authorities have behaved well".

"My interpretation is that this is a political and diplomatic matter that long ago rose above being just an intelligence matter," he said.

Assange said WikiLeaks had intervened to support Snowden, a 30-year-old former US National Security Agency contractor, because it had "the skills set and international network to do it" and it was a case of "practising what you preach".

He said Russia had always appeared to be a safer choice than Hong Kong, which he said WikiLeaks felt would have eventually moved to extradite the American back to the US and would have detained him in the meantime.

Former hacker Assange, who has said the US owes a "debt of gratitude" to Snowden for exposing the surveillance on Internet and telephone usage, hinted at more material from Snowden being made available.

"Hopefully one day, not too far in the future, we will see a WikiLeaks file rollout to media organisations," said Assange.

"Everything else being equal, material should be published as soon as possible... otherwise governments or agencies start to cover up, (and) work out how to prepare their spin."

Assange has been holed up at the Ecuador embassy in London for over a year after claiming asylum from that country to avoid extradition to Sweden, where he is wanted for questioning over allegations of sexual assault against two women.