AC Milan were left fuming Thursday when their highly-rated 18-year-old goalkeeper Gianluigi Donnarumma said he would not sign an extended contract with the Italian giants.

Considered the heir to Italy and Juventus goalkeeper Gianluigi Buffon, Donnarumma is a target for a number of top clubs and making him the pillar of the club's future with an extended contract had been Milan's number one priority.

"Mino Raiola (the player's agent) has just told me there will be no extension with Donnarumma and that the decision is definitive," the club's general manager Marco Fassone told reporters after a 40-minute meeting with Raiola.

"We are bitterly disappointed about the decision, but we move on, Milan move on."

Italian media have speculated the 'keeper will be sold this summer with Raiola citing interest from Real Madrid and Paris Saint Germain.