FISTS were flying in a US McDonald's branch as two female co-workers viciously beat each other while a six foot brute egged them on.

The bizarre brawl broke out behind the counter in Dekalb, Illinois, as a violent thug shouts "beat that b****".

The clip starts with two women grappling near the coffee machine before slamming into a drinks dispenser and slumping to the floor.

Other workers watch in shock as the pair trade blows, while a male with long black hair encourages them to "beat" each other.

The violence escalates as the man, wearing a Chicago Bulls top, weighs in and appears to try to grab one of the women.

Another female staff member manages to hold him off for a few seconds before he hurls her to the ground and lunges at the fighting duo.

He grabs one of the women and drags her away from the counter as others try to pull him away.

As he moves to leave, the worker he pushed shouts: "You hit a woman!"

He replies: "I hit you? F*** you shorty," before she tells him the whole thing was caught on CCTV.

Sun Online has contacted McDonald's for comment.