Susan Boyle was overcome with emotion after her fans threw her a surprise birthday party in Japan.

The 'Wild Horses' singer - who is currently in Tokyo promoting her album 'I Dreamed A Dream' - burst into tears as her admirers brought out a cake and sang 'Happy Birthday' in honour of her turning 49.

A source said: "She couldn't believe her eyes and burst into tears."

Linda Caillet, who helped organise the event, said: "This started out as a small idea. A couple of us asked if anyone wanted to go to see Susan sing in Japan and before long it became a big group of us from all over the world.

"One of the group flew over from Australia for a day to buy the tickets because you could only get them in Japan."

Guests donned home-made 'Susan Boyle' buttons and red scarves in tribute to the star.

They also gave her presents and Susan was left stunned by one gift - a £6,000 bracelet from her label boss Simon Cowell, who had the jewellery sent to the venue.

The source added: "She had seen the bracelet in a magazine and said, 'Gosh, imagine owning something like that.' So Simon tracked it down at Harrods."

Susan - who turns 49 today (01.04.10) - will also receive another birthday present, a £4 million payout from Simon's record label SyCo.

The payout is the first instalment of royalties from her hugely successful debut album, which became the fastest-selling LP in British chart history, with more than 3.1 million copies bought in its first four weeks.

The LP has sold more than 8.5 million copies worldwide.