WikiLeaks founder Julian Assange is keeping busy inside Ecuador's London embassy by working on his computer, exercising on a treadmill and cooking food in his microwave, according to friends.

Vaughan Smith, a former army officer who hosted 41-year-old Assange at his English mansion for more than a year while the Australian was under house arrest, said conditions in the embassy were basic, but comfortable enough.

"It's not worse than a prison cell, for sure," Smith told AFP. "The primary reason that it's not worse is that he can use a computer and the Internet. He can work, and that is his prime concern."

Assange has not left the embassy in a chic district of London since June 19, when he claimed political asylum in a bid to avoid extradition to Sweden where he is wanted for questioning over alleged sex crimes.

He claims he could be passed from Sweden to the United States -- which WikiLeaks enraged in 2010 by publishing a vast cache of diplomatic cables as well as secret files on the wars in Iraq and Afghanistan -- and prosecuted.

Ecuador granted asylum to the former computer hacker last Thursday, but with Britain refusing to grant him safe passage out of the country, he remains shut inside as the diplomatic standoff rumbles on.

Smith, who visited Assange last week, said he had a small running machine to exercise on, a shower, and a microwave to heat his food at the embassy, which occupies a flat in a redbrick Victorian building.

"His kitchen facilities are certainly rudimentary," said Smith, laughing as he added that Assange was probably not getting his food from the luxury Harrods department store, which is just around the corner.

"I think he's paying for his own food, and he doesn't have that sort of money," he said.

He added that Assange has divided his small room into an office and a living area, and was keeping it "rather cleaner and tidier than I recall him being, actually."

"It's certainly clean and tidy for an ex-hacker," he laughed.

"He can have visitors and he can carry on his activities. He has quite a lot to resolve -- he's fighting court battles against Visa and MasterCard, there's this whole Swedish matter, and there's trying to run WikiLeaks."

Credit companies have refused to handle donations to the website.

Smith said he remained on good terms with Assange despite standing to lose the £20,000 ($31,000, 25,000 euros) he put up for the WikiLeaks founder's bail in 2010 after he was arrested over the sex crime allegations.

"It's not clear that I have lost my money yet," Smith told AFP. "This kind of matter is considered by a magistrate, and it is surely a factor that he has claimed and received political asylum. It may well have an important bearing."

WikiLeaks spokesman Kristinn Hrafnsson, who has visited his colleague regularly over the last two months, said Assange's room gets some sunlight through the window.

Media have also reported that Assange -- who looked in good health as he appeared on the embassy balcony on Sunday to address hundreds of supporters -- has been sitting under an artificial "sun lamp" while cooped up inside.

"He is not unaccustomed to living under rough circumstances," Hrafnsson told AFP by telephone from Iceland.

Assange hopped from city to city after WikiLeaks was founded in 2006, often sleeping on friends' sofas.

"He can of course walk around in the embassy's territory," said Hrafnsson. "He is in good spirits."