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Justin Bieber beat the crap out of one of his Israeli bodyguards ... and berated the former soldier after a disagreement ... this according to a new lawsuit.

Biebs -- who's 5'7" and MAYBE 130 lbs -- is being sued by Moshe Benabou, an ex-member of the Israeli army.

According to Benabou -- who claims he worked for the singer from March 2011 to Oct. 2012 -- JB berated him and punched him in the chest multiple times during a disagreement about how to handle a member of Bieber's entourage.

Benabou is seeking unspecified damages for assault and battery -- and more than $420,000 in unpaid overtime.

But sources in Bieber's camp tell TMZ ... Moshe is nothing more than a "disgruntled employee looking for money." They say the claim that Bieber struck him is "absurd."

As for why Moshe was fired, our sources say he told multiple lies including a big one -- that he had worked closely with Justin Timberlake before being hired by Bieber.

Our sources say it was discovered that he never worked for JT a day in his life.

You may recall, Benabou was the guy who got into a physical confrontation with a photog at LAX back in February. After a brief struggle, both men fell to the ground ... and Benabou landed a pretty solid punch while the pap was being restrained by another person.

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