Controversial documentary maker Michael Moore has risked sparking outrage by branding military snipers "cowards".

The Fahrenheit 9/11 director took to social media over the weekend (17-18Jan15) following the release of Oscar-tipped movie American Sniper to insist crack shots who take out the enemy from a hidden position "aren't heroes".

In a post on Twitter.com, he wrote, "My uncle killed by sniper in Ww2 (sic). We were taught snipers were cowards. Will shoot u (you) in the back. Snipers aren't heroes. And invaders r (are) worse."

American Sniper, which has been nominated for six Academy Awards including Best Picture, stars Bradley Cooper as acclaimed U.S. Navy SEAL Chris Kyle, who endured four tours of duty in Iraq and notched up 160 confirmed kills. He died in an incident at a shooting range in Texas in 2013.

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Daily Mail: Michael Moore slams snipers as 'military assassins' | Daily Mail Online