'Intrusive, expansive' French surveillance laws failed to stop terror attacks: Snowden

French intelligence did not prevent the Paris attacks despite benefiting from "most intrusive" surveillance laws because suspects are "buried under data", US whistleblower Edward Snowden said on Wednesday.

"France passed one of the most intrusive, expansive surveillance laws in all of Europe last year and it didn't stop the attack," the former US intelligence contractor told Dutch state broadcaster NOS in an interview.

The French parliament passed a controversial law in December 2013 that facilitates police and intelligence agencies' access to telephone and Internet data in the fight against militants and organised crime.

Snowden, interviewed in Moscow where he has sought political asylum after revealing the US National Security Agency methods, drew a parallel with the controversial post-9/11 Patriot Act.

Mass surveillance enabled by the act did not prevent the 2013 Boston marathon attacks, Snowden said, recalling a conversation with a colleague on the day of the bombings that killed 3 people and wounded 264, the worst attack in the US since 9/11.

"I said to him you know I'm willing to bet almost anything that we knew who these people were, that we had something on them, and later on we found out that was the case."

"The problem with mass surveillance is that you're burying people under too much data."