Sunderland have completed the signing of Greek winger Charis Mavrias from Panathinaikos for an undisclosed fee.

The 19-year-old Greece international has agreed a three-year deal with the Black Cats.

Mavrias made his Champions League debut as a 16-year-old in 2010 becoming the second-youngest player ever to figure in the competition.

The teenager has made 59 domestic and 11 European appearances for Panathinaikos scoring six goals.

He has also made two appearances for Greece having also appeared at Under-17 Under-19 and Under-21 levels for the national side.