NEW YORK - Edward Snowden, the former National Security Agency (NSA) contractor who blew the whistle on the US government's mass surveillance programs, has been reunited in Russia with his long-time girlfriend, a new documentary shown on Friday revealed.

Lindsay Mills, who was living with Snowden when he left Hawaii for Hong Kong in May 2013, joined him in Moscow in July 2014, the documentary "Citizenfour" disclosed in a surprise revelation.

The two are filmed cooking together in an apartment in Moscow, where Snowden has been living since he was given temporary asylum and later a three-year residency permit.

Mills had remained silent and her whereabouts were largely unknown after Snowden's release of tens of thousands of classified US intelligence documents in 2013.

"Citizenfour," made by film maker Laura Poitras, had its world premiere at the New York film festival on Friday.

It gives a fly-on-the wall account of Snowden's tense days in a Hong Kong hotel and his encounters with journalists from the Washington Post and Britain's Guardian newspaper as they prepared to divulge details of NSA programs that gathered data from the Internet activities and the phones of millions of ordinary Americans and dozens of world leaders.