Revellers at the Lollapalooza music festival in Chicago were delighted to see Rihanna join Eminem on stage when he headlined the event on Friday.

And the Bajan pop princess performed the vocal part in his breakthrough hit Stan, as well as teaming up with Marshall Mathers III for their joint hits The Monster and Love The Way You Lie.

The event gives fans a sneak preview of their joint headline mini-tour - The Monster Tour: Eminem X Rihanna - which starts in just a few days.

The Monster is in contention for Best Male Video, Best Collaboration and Best Direction at this year's MTV Video Music Awards.

This year's Lollapalooza also features sets from Outkast, Arctic Monkeys, Kings Of Leon and Calvin Harris.