ITALY (REUTERS) - AC Milan goalkeeper Gianluigi Donnarumma has stunned the club by turning down a new contract, Milan chief executive officer Marco Fassone has said.

Donnarumma signed for Milan's youth team in 2013 before making his senior debut in 2015 at just 16-years-old.

He went on to become first-choice keeper at the club, making 68 appearances over the last two seasons.

The 18-year-old's contract expires next year and his decision to reject a new deal was made on Thursday after talks between the player, his agent Mino Raiola and the club.

"Raiola informed us that Donnarumma has made a definitive decision not to renew the contract with Milan," Fassone said in a statement.

"We were taken by surprise, as we had hoped Donnarumma would be the goalkeeper taking Milan into the future. Naturally, the decision leaves a bitter taste in the mouth, but now we have to go forward."

The Italy international made his under-21 debut in 2015 and was called up to the senior side in 2016.