Clint Eastwood's controversial war drama American Sniper is smashing records and expectations at the North American box office, with four-day earnings expected to surpass $105.3 million US.

The movie, which stars Bradley Cooper as real-life U.S. Navy SEAL Chris Kyle, is also set to become the biggest film ever to open on the Martin Luther King Jr. long weekend in the U.S.

"It's become a cultural phenomenon," said Dan Fellman, head of domestic distribution for Warner Bros. "The movie reached an audience that's very hard to tap into. In both red and blue states, small and large cities, tiny towns — everywhere we went — it broke records."

The box office blowout also gives American Sniper the second-biggest debut weekend of all time for an R-rated movie, according to financial magazine Forbes. The top spot is still held by sci-fi action flick The Matrix Reloaded.

Sniper attracts accolades and criticism

The record weekend is just the latest coup in a series of successes for the movie. American Sniper surprised last week with a respectable six Academy Awards nominations, including best picture and best actor for Cooper. 

But along with the accolades there has been criticism that the film glorifies a killer.

American Sniper is based on Chris Kyle's bestselling memoir that recounts his journey from being a rodeo cowboy to a trained sniper credited with 160 kills. He was honourably discharged in 2009 after 10 years of service, including four tours in Iraq. 

Actor Seth Rogen took to Twitter to compare Eastwood's Iraq war drama to Nazi propaganda. "American Sniper kind of reminds me of the movie that's showing in the third act of Inglorious Basterds," wrote the Canadian comedian.

'Snipers are cowards'

Documentary filmmaker Michael Moore pointed out the irony of releasing a movie about a sniper on the Martin Luther King Jr. holiday weekend.

Oscar Nominations Bradley Cooper American Sniper Jan 15 2015

Bradley Cooper stars in American Sniper. The R-rated Warner Bros. movie smashed expectations during in its first weekend in theatres. (Warner Bros. Pictures/Associated Press)

​"Lots of talk about snipers this weekend (the holiday weekend of a great man, killed by a sniper)," the Bowling For Columbine director wrote on Facebook Sunday.

"My uncle, Lawrence Moore, was an army paratrooper and was killed by a Japanese sniper 70 years ago next month," said Moore, who revealed that his dad taught him that "snipers are cowards." 

"Only a coward will shoot someone who can't shoot back," Moore wrote, quoting his father.

As for the movie, Moore called Cooper's performance "one of the best of the year," but that it was "too bad Clint [Eastwood] gets Vietnam and Iraq confused in his storytelling. And that he has his characters calling Iraqis 'savages' throughout the film." 

Michael Moore

Documentary filmmaker Michael Moore weighed into the debate, noting that he was raised to believe snipers are cowards. (Jonathan Alcorn/Reuters)

Further criticism for the film came from New Republic reporter Dennis Jett who argued that American Sniper attempts to add more nuance to the thinking Kyle expressed in his book.

"Eastwood's film … tries to make a straightforward situation more complex than it is," Jett said in a recent commentary in the left-wing American publication.

"Anyone who has read Kyle’s autobiography of the same title knows that his bravado left no room for doubt. For him, the enemy are savages and despicably evil. His only regret is that he didn’t kill more."

Kyle was shot and killed at a Texas gun range along with another man in 2013. Iraq War veteran Eddie Ray Routh is facing a murder charge in Kyle's death. His trial starts next month. 

With files from The Associated Press