Justin Bieber strips naked, serenades grandma

TMZ has unveiled yet another shirtless picture of Justin Bieber. However, this time the 19-year-old star is also pantless.

The photos show a birthday-suited Bieber covering his privates with a guitar as he walks around his grandmother Diane Dale's Toronto home. They were reportedly taken in November 2012 as the singer celebrated Thanksgiving with his family.

According to the source who released the photos to TMZ, the singer had been staying over at his granny's during the holiday and decided to prank her and the rest of his family by serenading them in the nude.

One of the photos shows Bieber's naked derriere as he sings to his grandmother who is another room. He reportedly belted out impromptu lyrics like, "I Loooove you grandmaaaa ... how are youuuu ... helloooo grandma."

Grandma reportedly thought Bieber's stunt was really funny, but soon asked him to put on some clothes.

Last month, Dale told Canada's CTV she "felt sorry for Justin all the time because paparazzi pick on him all the time." However, it looks like this time it was his own family who went behind his back to release the images.

Neither Bieber or his management team have commented on the pictures.