AceShowbiz - Teen sensation Justin Bieber has been learning how to land a left hook from British boxing champion David Haye. The "Baby" hitmaker shed his clean-cut image and stepped into the ring with the current World Heavyweight Champion at his training gym in London on Sunday, March 13.

And Haye admits he was impressed with his opponent's punching skills, writing in a post on his Twitter.com page, "Great workout in The Hayemaker Boxing Gym, Justin Bieber. You sure can pack punch!! I'm now a Belieber! Stay Blessed!"

Meanwhile, Justin gushed, "Worked out with Boxing Heavyweight Champion of the World David Haye. I took it easy on him. haha. good times (sic)."

It's not the first time the boxing giant has taken on a pop heavyweight - he sparred with rapper Dizzee Rascal earlier this year.