Rihanna's rumoured boyfriend surprised her with a 22nd birthday party at the weekend.

The 'Rude Boy' singer was 'shocked' by the bash put together by baseball player Matt Kemp in Phoenix, Arizona - where Kemp is currently training - as she was only expecting a small gathering of friends.

A source said: 'It was so sweet and she was really surprised. She looked just beautiful.'

Matt organised Caribbean food to be served to Barbados-born Rihanna and also reportedly bought her a custom-made diamond necklace.

The party was extra-special for Rihanna as she cancelled her 21st birthday celebrations last year in the aftermath of her assault at the hands of then-boyfriend Chris Brown early in February 2009.

The source said: 'Matt really wanted to do something nice for Rihanna this year since she didn't have much of a 21st birthday last year. It was just her closest friends, good Jamaican food, a photo booth, dancing and a nice cake.' Matt, 25, has been linked to Rihanna since they were seen holidaying together in Mexico in January, but he has played down romance rumours.

He said: 'Rihanna is just a friend, a good friend of mine. We went down to Mexico and had fun together.'