Australia's prime minister slammed WikiLeaks' publication of classified documents as "illegal" on Thursday, in the country's strongest condemnation yet of the website's ongoing release of sensitive data.

Julia Gillard's comments, while tough, did not indicate Australia was about to take legal action against Australian-born WikiLeaks founder Julian Assange. The country's attorney general reiterated Thursday that authorities are investigating whether Assange has broken any Australian laws, but have not yet reached a conclusion.

"I absolutely condemn the placement of this information on the WikiLeaks website," Gillard told Fairfax Radio. "It's a grossly irresponsible thing to do and an illegal thing to do."

On Sunday, WikiLeaks released thousands of U.S. diplomatic memos, enraging federal officials and prompting other countries to question whether the U.S. could be trusted.

On Monday, Australian Attorney General Robert McClelland said police were investigating whether WikiLeaks had broken any Australian laws with its latest document dump. Following Gillard's comments Thursday, a spokesman for McClelland confirmed the investigation is ongoing.

Assange, 39, has not been seen in public since a Nov. 5 news conference in Geneva. This week, a European arrest warrant was issued for him on Swedish rape charges.

McClelland said Wednesday that Australia would detain Assange if possible in response to the Interpol warrant, as required under international agreements.

The attorney general said he was not aware of any request from the U.S. to cancel Assange's Australian passport.