Rihanna was forced to seek medical attention after being assaulted by a crazed fan.

The "Stay" singer was targeted in an unprovoked attack by a man, who hurled a bottle of Lucozade at her, while leaving exclusive London nightclub The Box with her model pal Cara Delevingne on Saturday night. The force of the glass bottle caused the 24-year-old star to fall and cut open her knee.

Her bodyguard's leg was also said to have been injured as he attempted to catch her attacker, who allegedly shouted something about Rihanna's boyfriend Chris Brown before throwing the bottle at her.

According to MediaTakeOut.com, "The bottle caused Rihanna to stumble into a metal drate - and slice open her leg. Rihanna's bodyguard immediately went after the crazed fan but hurt his leg going after the subject. Rih's guard was taken to a London hospital for treatment, and the mad man is still on the loose."

Rihanna, who was in London to launch her fashion line for River Island at London Fashion Week yesterday, was seen clutching her injury but it did not appear to be serious.