The man who claimed to leak state secrets on U.S. government eavesdropping sought to break the story through a columnist for a U.K.-based publication who has made no secret of his distaste for intrusions on privacy.

Edward Snowden, 29, brought his information first to Glenn Greenwald of The Guardian, illustrating the passion an opinion-driven journalist can bring to a breaking news story at the same time it raises questions about fairness.

In other developments:

Booz Allen Hamilton Holding Corp. said it has fired Edward Snowden, who worked as an infrastructure analyst for the company in Hawaii. He was terminated Monday "for violations of the firm's code of ethics and firm policy," according to a statement on its website. He had been paid at a rate of $122,000 a year, it said. The firm called Snowden's actions "shocking" and said he had been a Booz Allen employee for less than three months.

The U.S. government is filing charges against Edward Snowden, CBS News reported, citing unnamed sources. Their nature and scope remain to be seen. Snowden was last reported to be in Hong Kong, from which he could technically be extradited by the U.S.

Pentagon Papers leaker Daniel Ellsberg called Snowden's revelations the most "significant disclosure" in the nation's history. Ellsberg, who in 1971 passed the secret Defence Department study of U.S. involvement in Vietnam to the New York Times and other newspapers, said Monday that the leaks by Edward Snowden to the Washington Post and the Guardian newspapers are more important than the Pentagon Papers and information given to the anti-secrecy website WikiLeaks by Army intelligence analyst Bradley Manning.

Greenwald said Tuesday that there will be more "significant revelations" to come from the documents. "We are going to have a lot more significant revelations that have not yet been heard over the next several weeks and months."

Greenwald told The Associated Press the decision was being made on when to release the next story based on the information provided by Edward Snowden, an employee of government contractor Booz Allen Hamilton who has been accused by U.S. Senate intelligence chairwoman Senator Dianne Feinstein of California of committing an "act of treason" that should be prosecuted.

Greenwald, author of three books in which he argues the government has trampled on personal rights in the name of protecting national security, wrote the original stories exposing the extent of the government's data collection.

Great public interest

Over the weekend, he identified intelligence contractor Snowden as his source at Snowden's request, and said more stories are coming.

"What we disclosed was of great public interest, of great importance in a democracy, that the U.S. government is building this massive spying apparatus aimed at its own population," Greenwald said Monday on MSNBC's Morning Joe.

Photos of Edward Snowden, a contractor at the National Security Agency (NSA), and U.S. President Barack Obama are printed on the front pages of local English and Chinese newspapers in Hong Kong June 11. Snowden, who leaked details of top-secret U.S. surveillance programs, dropped out of sight in Hong Kong on Monday ahead of a likely push by the U.S. government to have him sent back to the United States to face charges. (Bobby Yip/Reuters)

Greenwald also told The Associated Press that he's been contacted by "countless people" over the last 24 hours offering to create legal defence funds for Snowden.

The topic is personal for Greenwald, 46. The former constitutional and civil rights lawyer, educated at the New York University Law School, began the "Unclaimed Territory" blog in 2005 and wrote How Would a Patriot Act? a year later. The book criticized the Bush administration for its use of executive power.

Greenwald, now based in Brazil, wrote a regular column for Salon for five years until joining The Guardian last year. He said he wanted to reach a more international audience, a desire that coincided with the news organization's effort to expand its reach in the U.S. market.

One program he wrote about collects hundreds of millions of U.S. phone records. The second program takes in audio, email and other electronic activities primarily by foreign nationals who use providers like Microsoft and Apple. Greenwald described the collection of phone records on Monday as "rampant abuse and it needs sunlight. That's why this person came forward and that's why we published our stories."

On Morning Joe, he snapped that co-host Mika Brzezinski was using "Obama talking points" when she challenged him with a question.

"The wall of secrecy behind which they operate is impenetrable and it is a real menace to democracy," said Greenwald, who won a 2010 Online Journalism Association award for his coverage of Bradley Manning, who is charged with giving classified documents to WikiLeaks.

Snowden, however, had not just gone to Greenwald with his information. Barton Gellman of The Washington Post wrote on Sunday that Snowden had contacted him about the story. He said Snowden had asked that the Post publish within 72 hours the full contents of a presentation he had made about the collection of electronic activity from the Silicon Valley companies.

Clear point of view

Gellman said the Post would not make any guarantees and sought the government's views about whether the information would harm national security. The Post eventually agreed to publish a small sample of what Snowden was offering, but Snowden backed away, writing that "I regret that we weren't able to keep this project unilateral," Gellman wrote.

He then contacted Greenwald, the Post said.

Greenwald's clear point of view doesn't necessarily weaken the story, said Jay Rosen, journalism professor at New York University and author of the Press Think blog.

"In many ways it strengthens it," he said. Greenwald has a clear stance on privacy and national security, but they aren't partisan; he's criticized Democratic President Barack Obama and his Republican predecessor, George W. Bush. Journalists who have strong viewpoints is a tradition with a long history in the U.S., Rosen said.

Little opening for critics

"The fact that sources now may choose (outlets) on the basis of commitment is a fact and journalists whose professional stance is no commitment may find themselves at a disadvantage," he said.

Greenwald's known feelings on the issue "does leave a little opening for critics," said Ellen Shearer, head of the national security journalism initiative at Northwestern University. There's always a risk that such passion can work against a journalist; some people would worry that facts contradictory to a predisposed belief could be overlooked.

To this point, Shearer said there's been little pushback on the facts, with the debate primarily about whether the information should be published.

Intelligence officials are investigating the leak and its impact on its programs. Director of National Intelligence James Clapper called the revelation of the intelligence-gathering programs reckless and said it has done "huge, grave damage."

Concealed from public

The Guardian took care not to publish material that may help other countries improve their eavesdropping or could put the lives of covert agents at risk, Greenwald said.

"We've published these things they marked 'top secret' that don't actually harm national security but conceal what they've done from the public," he said.

The story is a coup for the Guardian, a U.K.-based independent news organization that started covering the United States more aggressively when it determined that one-third of its web traffic came from the U.S. Offices in New York and Washington were opened in 2011, and the Guardian now has 57 employees in the U.S.

The Guardian doesn't offer its newspaper for sale in the U.S., but web traffic to its news website in the U.S. market has increased 47 per cent over last year and is likely to jump further with this month's exposure.