U.S. federal authorities have begun to investigate whether WikiLeaks founder Julian Assange could be charged under the Espionage Act for releasing secret diplomatic documents, media sources reported on Tuesday.

The Australian citizen, whose online whistleblower organization created a world-wide storm with its vast revelations, has been hiding in London to evade questioning over allegations that he assaulted two women in Sweden.

Open gallery view WikiLeaks founder Julian Assange in Stockholm, Sweden in August 2010. Credit: AP

Ecuador has offered Assange asylum, "with no problems and no conditions," the South American country's Deputy Foreign Minister Kintto Lucas told the Internet site Ecuadorinmediato.

The Penatagon and the Justice Department are in the midst of an "active, ongoing criminal investigation," The Washington Post quoted U.S. attorney General Eric H. Holder Jr. as saying.

Holder did not indicate to The Post whether Assange would indeed be charged for violations of the Espionage Act, nor whether such an indictment was imminent.

Should the U.S. bring such charges against Assange, authorities would need to extradite him from whatever country he was residing in at the time. Experts have said that it could be a difficult case, because of sensitivities regarding the First Amendment.

Former CIA general council Jeffrey H. Smith told The Washington Post, however: "I'm confident that the Justice Department is figuring out how to prosecute him."

In a phone video message late Monday, Assange accused President Barack Obama of stifling freedom of speech, calling the current administration “a regime that doesn’t believe in the freedom of the press and doesn’t act like it believes it”.