A previously unseen letter written by Pablo Picasso, complete with sketches, has gone on display in western France.

The letter, to his friend the French poet Max Jacob, comes from a private collection and is displayed at the fine arts museum in the western city of Quimper.

Beginning "my dear Max" and signed "your brother Picasso", the letter shows the close bond between the Spanish artist and Jacob, who was "his best friend at the time and the person who really discovered him", according to museum director Ambroise Guillaume.