Chris Brown's posse is accused of beating a woman so badly at a Vegas party she was hospitalized for whiplash.
Jakaria, a 28-year-old insurance agent, tells us she was hanging with Brown and his crew early Sunday at Palms Casino Resort. She says everyone had to leave their phones with his security, and when she went to pick up her 2 phones, his team thought she was trying to steal someone else's.
That's when Jakaria says Brown's security guard got violent, grabbing her by the hair, shaking her around and throwing her to the ground. She says the guard tried to stomp on her but someone mercifully stepped in.
Jakaria says she got home but realized she was in bad shape so she called an ambulance. Doctors told her she had whiplash.
Law enforcement sources tell TMZ cops took a battery report and they're looking into the incident.