An American student being held over the killing of Meredith Kercher is reportedly annoying warders and inmates in prison by singing.

Amanda Knox, 20, is said to constantly sing the Beatles classic Let It Be in jail in Perugia, Italy, where she has been for three months.

A source told The Sun: "From first thing in the morning till lights out, she is singing. It drives you mad."

The US student's request for a guitar was apparently turned down.

Meredith was living and studying in the Italian town of Perugia when she was killed.

The 21-year-old was found semi-naked with her throat cut on November 2.

Knox, Raffaele Sollecito, 24, and Rudy Guede, 20, deny they were involved in the death of the Leeds university student.