NSA whistleblower Edward Snowden has denied he committed treason with his revelations that the US had been hacking Hong Kong and China since 2009. He said his revelations did not disclose military targets - a treasonable act - only civilian infrastructure.

"I pointed out where the NSA has hacked civilian infrastructure such as universities, hospitals, and private businesses because it is dangerous," he said during a Q&A session with Guardian readers.

"These nakedly, aggressively criminal acts are wrong, no matter the target."

The 29-year-old former National Security Agency contractor and source of the Guardian's scoop about systematic data trawling by the US government said: "Without asking for public permission, the NSA is running network operations that affect millions of innocent people.".

In a previous interview with the South China Morning Post, Snowden said he was releasing the information to demonstrate "the hypocrisy of the US government when it claims that it does not target civilian infrastructure, unlike its adversaries".

Direct access?

Snowden also attempted to clarify a key but obscure point reported by the Washington Post and the Guardian. Internet companies - including Facebook, Google, Yahoo, Apple and Microsoft - were reported to have given the NSA "direct access" to their servers under a data collection programme called Prism.

Most companies have denied involvement with the programme. Apple, for example, claimed it does not provide "any government agency" with direct access to its servers. "Any government agency requesting customer content must get a court order," it said.

Facebook said it received 9,000-10,000 requests for user data from US government agencies in the second half of 2012 but granted only a handful.

Snowden reiterated claims that all US government agency had access to the raw databases of these companies. "They can enter and get results for anything they want [such as] phone numbers, email, user id, cell phone handset id," he claimed.

"The restrictions against this are policy-based, not technically based, and can change at any time" he warned. " Additionally, audits are cursory, incomplete, and easily fooled by fake justifications. Fr GCHQ, the number of audited queries is only 5% of those performed. "

Snowden said the web companies were "legally compelled to comply and maintain their silence.

He accused Washington of destroying any possibility of him getting a fair trial.

"[They] openly declaring me guilty of treason and [said] that the disclosure of secret, criminal, and even unconstitutional acts is an unforgivable crime," he said.

He explained that he opted for Hong Kong instead of Iceland after leaving Hawaii, where he was working at an NSA office, because he was afraid of being arrested en route.

"I had to travel with no advance booking to a country with the cultural and legal framework to allow me to work without being immediately detained," he said.

"Hong Kong provided that. Iceland could be pushed harder, quicker, before the public could have a chance to make their feelings known, and I would not put that past the current US administration. "

Snowden voluntarily came forward as the person who leaked the documents to the Guardian and Washington Post newspapers about the Prism programme.

Snowden is a former technical adviser for the CIA and has been working for the past four years at the NSA. He was employed by several outside contractors including his current employer, defence contractor Booz Allen Hamilton.