London, Feb 19 : Rihanna's 20th birth anniversary was certainly a sweet bash what with the singer and her guests ending up throwing cake on each other.

The US R'n'B star celebrated her birthday by pelting guests with cupcakes, but ended up getting splattered by pals including Kanye West and actor Wilmer Valderrama.

A spy at the Les Deux club in LA revealed that the singer's face was full of frosting.

"There was frosting all over Rihanna's face and the group was laughing to the point of almost tears!" the Mirror quoted the source, as saying.

An onlooker added: "There was cupcake frosting all over Rihanna's face and the group was hysterically laughing to the point of almost tears!"

ANI