A star American football player has accused the Las Vegas police of using excessive force, pointing their firearms at him and threatening to kill him because he is African-American.

In a Twitter post, Michael Bennett wrote that he had left a heavily publicised fight between Conor McGregor and Floyd Mayweather when he heard gunshots and began to run away.

After Las Vegas police officers stopped him, Mr Bennett wrote, one officer pointed a gun at him and warned that he would “blow my…head off” if he moved.

Floyd Mayweather vs Conor McGregor in pictures Show all 14 1 /14 Floyd Mayweather vs Conor McGregor in pictures Floyd Mayweather vs Conor McGregor in pictures Post-fight Floyd Mayweather celebrates his victory over Conor McGregor. Getty Floyd Mayweather vs Conor McGregor in pictures Mayweather vs McGregor Conor McGregor arrives in the ring first. Getty Floyd Mayweather vs Conor McGregor in pictures Round 1 McGregor shot out of the blocks to take the fight to Mayweather. Getty Floyd Mayweather vs Conor McGregor in pictures Round 2 McGregor looked calm and in control as he took the opening round. Getty Floyd Mayweather vs Conor McGregor in pictures Round 3 Mayweather started to fight back from the third round. Getty Floyd Mayweather vs Conor McGregor in pictures Round 3 McGregor was struggling to contain Mayweather and was warned numerous times by the referee. Getty Floyd Mayweather vs Conor McGregor in pictures Round 4 The UFC star struggled with the pace of the fight as his fitness levels waned. Getty Floyd Mayweather vs Conor McGregor in pictures Round 4 Mayweather was able to evade all of McGregor's attacks. Getty Floyd Mayweather vs Conor McGregor in pictures Round 5 Mayweather shoved McGregor after the ball at the end of the fifth. Getty Floyd Mayweather vs Conor McGregor in pictures Round 6 The Irishman started to glance regularly at the clock. Getty Floyd Mayweather vs Conor McGregor in pictures Round 7 Mayweather was landing big shots at will with McGregor showing no defence. Getty Floyd Mayweather vs Conor McGregor in pictures Round 8 More punishment was dished out on the eighth round. Getty Floyd Mayweather vs Conor McGregor in pictures Round 9 The fight was nearly stopped in the ninth as Mayweather had McGregor on the ropes. Getty Floyd Mayweather vs Conor McGregor in pictures Round 10 Referee Robert Byrd eventually waved off the fight in the tenth round. Getty

Another officer “forcefully jammed his knee into my back making it difficult for me to breathe”, the Seattle Seahawks player wrote, and then “cinched the handcuffs on my wrist so tight that my fingers went numb”.

The allegation, which has been shared well over 100,000 times, is likely to inflame an already-blazing debate over police officers using force on African-American suspects.

A mounting collection of video footage showing officers killing suspects helped birth the Black Lives Matter movement and has spurred calls for measures, like body cameras, to promote police accountability.

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Athletes playing America’s most popular sport have not stayed on the sidelines, with Mr Bennett joining other African-American players in kneeling during pre-game broadcasts of the national anthem as an act of protest.

Mr Bennett contended that he was subjected to harsh treatment “for doing nothing more than simply being a black man in the wrong place at the wrong time”, adding that officers released him once they realised he was a professional athlete and not “a thug, common criminal or ordinary black man”.

“Equality doesn’t live in this country”, Mr Bennett wrote.

In a press conference, Las Vegas Metropolitan Police Department Undersheriff Kevin C McMahill rejected that notion, saying an investigation was underway but stating that “I see no evidence that race played a role in this incident”.

According to Mr McMahill, officers encountered Mr Bennett after entering a casino to respond to an early morning report of an active shooter. After confronting a scene of chaos that included large groups of people running for cover, Mr McMahill said, officers saw Mr Bennett, who was “crouched down behind a gaming machine”, run out of the casino.

“They believed Bennett may have been involved in the shooting and they gave chase,” Mr McMahill said, adding that both officers drew their handguns while detaining Mr Bennett, who was unarmed.

The investigation will include combing through at least 126 videos from body cameras, Mr McMahill said, asking anyone with additional footage to come forward.