Justin Bieber stunned revelers at Los Angeles hotspot 1OAK in West Hollywood on Saturday night (30Jan16) with an impromptu concert.

The pop star hit the stage and sang What Do You Mean? before teaming up for a performance with pal Tyga.

Stunned by the reaction of the largely 20-something crowd, Bieber asked, "How many people thought you would like Justin Bieber?"

He wasn't the only chart star serving up an unexpected concert in Los Angeles on Saturday - Rihanna gave an impromptu karaoke performance of Mary J. Blige's Not Gon’ Cry hours earlier at Miguel’s Wildheart Motel.

She then teamed up with Miguel for a rendition of My Girl by the Temptations.