Ajax reportedly have already had a €2million bid for the 21-year-old turned down.
Sigthorsson has just a year left on his current contract at AZ Alkmaar, but the club has offered the youngster a new deal.
AZ Alkmaar technical director Earnest Stewart told Dutch newspaper Algemeen Dagblad: “I have listened to Danny (Blind, Ajax technical director) but we don’t have the intention to sell him.
“We have offered him a new deal.”
“There are many rumours about Kolbeinn,” Sigthorsson’s brother and agent Andri said. “That is logical as he is doing well.
“But first we will take a look at AZ’s offer. If Kolbeinn won’t accept it we will start looking further.”
