Washington: The father of fugitive US intelligence leaker Edward Snowden has written to his son, hailing him as a "modern-day Paul Revere" saving Americans from a tyrannical government.

Lon Snowden, writing with civil liberties lawyer Bruce Fein, on Tuesday drew on American Revolutionary spirit in defending his son for "refusing to bow to government wrongdoing or injustice".

Edward Snowden, 30, sparked an international uproar last month when, as a contractor with the National Security Agency, he divulged details about US surveillance programs that gather phone and internet data.

He reportedly remains stranded in the transit area of a Moscow airport, seeking asylum in various countries in a bid to win protection from American authorities, who have filed espionage charges against him.