Justin Bieber and girlfriend backstage at Hillsong conference

Justin Bieber and his rumoured girlfriend Hailey Baldwin have made their presence known at the Hillsong Conference in Sydney.

The popstar is in town as a delegate of the church with no scheduled performance, however he has put in some impromptu playing backstage.

The singer has been videoed playing the drums during a backstage jam to the Stevie Wonder song, Superstition, while Baldwin watches on.

"I'm lead singer," Baldwin jokes.

Bieber stays quiet until the end when he says: "more cowbell".

The singer and Baldwin are in town for the week-long Hillsong Church conference at Allphones Arena in Sydney.

"People come from across the world to Sydney each year to attend Hillsong Conference. Justin is here - like tens of thousands of others - as a delegate who is seeking to build stronger foundations into his life," a statement from Hillsong Church said.

"He is not participating in the conference in any other capacity."