Julian Assange, founder of whistle-blowing website Wikileaks, has admitted he had sexual relations with one of two Swedish women who have accused him of sex crimes.

Assange said he had consensual sex more than once with a woman who has accused him of molestation, the Daily Telegraph reported Friday.

'I say the same thing I have said the entire time. I have not done anything with these two women that was not completely voluntary from both parts,' he said.

Sweden's top prosecutor has reopened investigations into allegations of molestation from the woman and of rape by another Swedish female.

WikiLeaks published over 70,000 secret military files on Afghanistan in July in what US officials have called one of the biggest security breaches in US military history.

An official had withdrawn a rape probe against Assange, while allowing an investigation into lesser molestation charges to continue.

Assange said he had been warned by Australian intelligence that he could face a campaign to discredit him after leaking the documents. He said he was facing a smear campaign but could not be sure who was behind it or for what reason.

'Who was behind this, we do not know. Whether that turns out to be a smear campaign done by a couple of people for personal motives or ideological motives, or whether that is larger and involves geopolitical concerns or whether it is a mixture of all those, we do not know,' he said.

The women involved have rejected the suggestion they were acting at the behest of a hidden conspirator.