Justin Bieber joins Selena Gomez onstage

Justin Bieber thrilled fans on Sunday night by staging an impromptu performance at a concert by his girlfriend Selena Gomez.

Justin Bieber thrilled fans on Sunday night (24Jul11) by staging an impromptu performance at a concert by his girlfriend Selena Gomez.

Disney star Gomez played a gig at the OC Fair in Costa Mesa, California and the audience was stunned when she was joined onstage by Bieber midway through the show.

The Baby hitmaker gave Gomez a hug before launching into a medley of songs including his track Favourite Girl and the Justin Timberlake hit Cry Me A River, according to MTV.co.uk.

After the show, he took to Twitter.com to thank fans for their support before sending a message to Gomez telling her: "U did great tonight. Proud of u."

WENN.com