WikiLeaks co-founder Julian Assange has given his strongest indication yet about the next big leak from his whistleblower organisation.

There has been rampant speculation about WikiLeaks' next revelation following its recent release of a top secret military video showing an attack in Baghdad which killed more than a dozen people, including two employees of the Reuters news agency.

Bradley Manning, a US military intelligence officer based in Iraq, has been arrested on suspicion of leaking the video but it is also claimed that Manning bragged online that he had handed WikiLeaks 260,000 secret US State Department cables.

In an interview with the ABC's Foreign Correspondent, Mr Assange said cryptically of WikiLeaks' current project:

"I can give an analogy. If there had been mass spying that had affected many, many people and organisations and the details of that mass spying were released then that is something that would reveal that the interests of many people had been abused."

He agreed it would be of the "calibre" of publishing information about the way the top secret Echelon system - the US-UK electronic spying network which eavesdrops on worldwide communications traffic - had been used.

Mr Assange also confirmed that WikiLeaks has a copy of a video showing a US military bombing of a western Afghan township which killed dozens of people, including children.

He noted, though, it was a very intricate case "substantially more complex" than the Iraq material WikiLeaks had released - referring to the gunship video.

European news media are reporting that Mr Assange has "surfaced from almost a month in hiding", speaking at a freedom of information seminar at the European parliament in Brussels.

But during the course of the past month, Mr Assange has been talking to Foreign Correspondent for a program examining the efficacy of the WikiLeaks model.

"What we want to create is a system where there is guaranteed free press across the world, the entire world, that every individual in the world has the ability to publish materials that is meaningful," he said.

Whistleblower speaks

The program has also spoken directly to former computer hacker Adrian Lamo who blew the whistle on Bradley Manning after a boastful online discussion in which Lamo alleges the military intelligence adviser revealed himself as a significant WikiLeaks source.

"He proceeded to identify himself as an intelligence analyst and pose the question: What would you do if you have unprecedented access to classified data 14 hours a day seven days a week?" Mr Lamo said.

"He (Manning) was firing bullets into the air without thought to consequence of where they might land or who they might hit."

WikiLeaks has built an information repository it thinks is foolproof. Instead of secret documents physically changing hands, they are anonymously sent to digital drop boxes and stored on servers around the world. Finally, they are posted on the WikiLeaks site.

During Foreign Correspondent's assignment Mr Assange had been preparing to fly to New York to meet his hero - Daniel Ellsberg - the former US military analyst who leaked the Pentagon Papers which amounted to a devastating expose of the Vietnam War.

Instead, concerned about travelling in the US and attracting the interest of authorities, he used Skype to speak to the conference.

He told the crowd: "Leaking is inherently an anti-authoritarian act. It's inherently an anarchist act."

Mr Assange has been quoted as saying he feels perfectly safe in Europe, "but I have been advised by my lawyers not to travel to the US during this period".

Daniel Ellsberg, named by Henry Kissinger as "the most dangerous man in America", told Foreign Correspondent that Mr Assange was "a good candidate for being the most dangerous man in the world, in the eyes of people like the one who gave me that award".

"I'm sure that Assange is now regarded as one of the very most dangerous men and he should be quite proud of that."

Truth or Dare, Foreign Correspondent's examination of Julian Assange and WikiLeaks, airs tonight at 8PM on ABC 1