The mother of Australian-born WikiLeaks founder Julian Assange today expressed fear for her son's safety, saying the forces he was challenging had become "too big".

Christine Assange said her "highly intelligent" and curious son had been raised as a strongly ethical "seeker of truth".

But Assange said her son, now subject to a global Interpol arrest demand over rape charges in Sweden, had become "too smart for himself" and she now feared for his safety.

"He sees what he's doing as doing a good thing in the world, fighting baddies if you like," Assange told the Courier Mail, her local newspaper in Queensland.

"I'm concerned it's gotten too big and the forces that he's challenging are too big," she added.

The WikiLeaks chief, who is said to lead a spy-like life of rarely sleeping in the same place twice, has sparked a political storm by dumping about 250,000 secret US diplomatic cables onto the Internet.

His mother -- who according to the Courier Mail does not even own a computer -- defended the 39-year-old's actions as being driven by deep conviction, and said he had not always been destined for a career in computer hacking.

"He didn't actually come from a background of high technology, he came from a background of creativity and a love of learning and books," Christine Assange said.

"Whether you agree with what Julian does or not, living by what you believe in and standing up for something is a good thing."
 

She said Julian Assange had put his life on hold when he was just 18 to care for his newborn son, Daniel, who is now 20 and works as a software developer in the southern city of Melbourne.

"Jules put his life and university studies on hold to parent Daniel and be there for him," Christine Assange said.

"He's a very good father -- not many men of that age will fight for their kid, but he stepped up to the responsibility."

Julian Assange's marriage to Daniel's mother reportedly broke down and there was a protracted custody battle.

Christine Assange said the father and son had even attended the University of Melbourne together -- Julian studying mathematics and physics while Daniel, then aged just 15, began a degree in genetics.

She said her son had distanced himself from the family for their own safety, but disputed some unflattering portrayals given of him by critics and ex-colleagues.

"He was (a) lovely boy, very sensitive, good with animals, quiet and has a wicked sense of humour," she said.