Boston (Agencies): More stunning revelation has come to fore about WikiLeaks founder Julian Assange, who is battling an extradition case over sexual misconduct.

Former WikiLeaks spokesman Daniel Domscheit-Berg has revealed in his upcoming book that the 39-year old Assange used to boast about how many children he has fathered across the world.

"Often I listened to Julian boast about how many children he had fathered in various parts of the world. He seemed to enjoy the idea of lots and lots of Julians, one on every continent.

"Whether he took care of any of these alleged children, or whether they existed at all, was another question," Domscheit-Berg, who left the organisation amid tensions with Assange, writes in his book, an excerpt of which was leaked to gossip website Gawker.

Last month, Daniel launched a rival site OpenLeaks.

"From his bombastic OKCupid profile to his creepy love letters to a 19-year-old girl, Wikileaks founder Julian Assange's has some strange romantic proclivities. Strangest of all is his apparent obsession with littering the world with offspring," Gawker reported.

According to leaked police documents on Assange's ongoing rape and sexual molestation case, WikiLeaks volunteer and Swedish journalist Donald Bostrom has told investigating officials in Sweden that Assange had "at least" four children.

This was a number "independently confirmed" to it by a former WikiLeaks volunteer and a former friend of Assange, Gawker said.

The US government has also been trying to put on trial Assange for spying after his whistle-blower website released thousands of secret documents on the wars in Iraq and Afghanistan as well as a flood of state department cables. No specific charges against him have been framed.