A "profound difference" has occurred over the past two years, following the leaking of NSA documents that led to revelations about US surveillance on phone and internet communications, whistleblower Edward Snowden has said.

Writing in the New York Times, the computer analyst said that the balance of power is changing as a post-terror generation "turns away from reaction and fear in favour of resilience and reason".

Snowden said that bulk data collection programmes had been declared illegal and disavowed by the US Congress.

"After a White House-appointed oversight board investigation found that this program had not stopped a single terrorist attack, even the president who once defended its propriety and criticised its disclosure has now ordered it terminated," he said in the piece, also published in the French newspaper Liberation.

Snowden said the achievement was driven by "the power of an informed public" and added the end of the mass surveillance of private telephone calls under the US Patriot Act was a "landmark victory for the rights of each citizen".