American singer Jason Derulo.

American R&B sensation Jason Derulo could be soon entangled in a bitter lawsuit after a brawl with a fan in a mall.

Accompanied by his security detail, the Whatcha Say crooner got enraged when a fan called him Usher.

“Hey, Usher. Well F**k you!” the fan standing metres from Jason yelled.

This did not go well with the star as he unexpectedly turned on the fan, swinging blows and sending him on the ground.

So angered was the star that not even his security detail could control him as he slipped from their grip and continued throwing blows as the crowd watched in shock.

Jason Derulo filmed beating up a fan. (Courtesy/TMZ)

According to the International Press, the attack could escalate into a nasty lawsuit. Nonetheless, his fans blamed the name-calling passerby who clearly aggravated the star.  

Here's the video of the altercation (Courtesy/Shaderoom);