Update: In an odd move, Katy Perry has apologised to Chief Keef following their twitter dispute. Perry tweeted: "Mr. Keef! I'm sorry if I offended you. I heard a lot of people guesting on the song & didn't even know it was you in particular. Actually.."

Great message to send.

Following Katy Perry's tweet displaying her "serious doubt for the world" prompted by Chief Keef's 'Hate Being Sober'; the rapper took to the social networking site to vent his anger.

In a series of offensive and distasteful outbursts, Chief Keef threatened to "smack the shit out of her" amongst other obscenities. The rapper - real name Keith Cozart - has been arrested previously on weapons charges and disorderly conduct. Check out the song that started it all below.