London, Aug 13 - Pop diva Madonna surprised her son Rocco, who turned nine Tuesday, when she urged a 50,000-strong crowd at her show in Denmark to sing 'Happy birthday' to him.

The 'Music' hitmaker is currently on her ongoing 'Sticky & Sweet' global tour and it was during her Denmark performance when she announced Rocco's ninth birthday to gig-goers and encouraged the crowd at the Parken Stadium to sing a chorus of 'Happy birthday' for the delighted youngster, reports express.co.uk.

She shouted out: 'Happy Birthday to my son Rocco, who is watching the show right now and I just want to say that I love you very much. You are a number one son and maybe everyone would like to sing 'Happy birthday' to him.'