Stevie Wonder and Chaka Khan performed Prince's hit single 1999 at a tribute concert to the late musician in front of thousands of fans.

Friends and former bandmates of Prince performed at the concert at the Xcel Energy Center in St. Paul, Minnesota on Thursday night.

Some 17,000 people attended the sell-out show in memory of the seven-time Grammy winner, who died of an accidental painkiller overdose in April.

Singer Christina Aguilera had cancelled her scheduled appearance as she fights a "vocal illness", and was replaced by British singer Jessie J.

Aguilera said in a statement: "It is with a heavy heart that I cannot perform this evening and join the amazing talent on stage to pay tribute to the legend that was Prince. He will remain in our hearts and inspire our music until the end of time."

John Mayer also bowed out of the concert earlier, citing a "change of schedule".

Before the concert, St Paul mayor Chris Coleman read a proclamation on the outdoor plaza declaring Thursday 'Prince Day' in Minnesota's capital.