Justin Bieber pretty much causes mass hysteria wherever he goes these days, so imagine the chaos he caused when he decided to perform an ‘off the cuff’ acoustic version of his smash hit ‘Boyfriend’ to a few hundred fans!

The star had just taped an interview with US chat show host Jay Leno when he pulled up alongside his devoted followers to sing for them.

Despite Justins efforts, his voice can hardly be heard above the screaming masses!

Check out the clip right here courtesy of Celebrity TV….