Grammy award winning Barbadian singer Rihanna celebrated her 20th birthday with much fanfare and a cupcake fight.

The 'Umbrella' singer turned 20 on Wednesday and partied with friends including International Rap sensation Kanye West and actor Wilmer Valderrama at Los Angeles' Les Deux nightclub when the food fight began.

Chris Brown, who is rumored to be dating Rihanna, was later given a standing ovation after he sang her an acapella version of 'Happy Birthday'.

Brown insists he and Rihanna are just friends, but onlookers at the exclusive club said the pair cuddled and they looked very cozy. The couple attended the Grammys together last weekend and stocked up on goody bags.

Rihanna picked up Balenciaga sunglasses, while Brown, 18, took home two pairs of Marc Jacobs sunglasses in red and blue.

When they realized they might be photographed together, Chris insisted they should leave.

A source close to the couple at the time said, "Chris was telling her they needed to go, and in seconds they were gone."