Mystic River actor Sean Penn has married 28-year-old Australian actress Leila George in a secret ceremony after a four-year relationship.

This is the third marriage for the Oscar winner Penn, who was previously married to Princess Bride actress Robin Wright and pop star Madonna.

A friend of the couple posted a picture of the pair with a cardboard cut-out of a wild cat and also a picture of two hands wearing wedding rings.

A friend of the couple wrote on Instagram: ''We are so happy for @leilageorge #seanpenn getting married. We love you. Thank you for being like family a son to mike we are over the moon to find your soul mate true partner @coreresponse true love that also changes the world for better

''You are meant to be together God Bless you both and the family you have joined. Introducing the Penn's #marriage."