As the rocker squatted mid-song during the first track of his set at Stockholm's Grona Lund themepark, his leather trousers ripped and revealed what appeared to be his manhood dangling between his legs - and the picture of the mad moment has now gone viral.

Fans claim Kravitz exited the stage for several minutes shortly afterwards and reappeared in a new pair of trousers.

One onlooker tells Expressen, "The producer stepped up and said that they had some problems on stage. A bit later Kravitz came out wearing other trousers. He said, 'Sorry, I ripped my trousers'."