'Sky Sports' is reporting that the goalkeeper will undergo a medical at the Eredivisie side tomorrow, after signing a new one-year contract with his new club.
There appears to be somewhat of a cycle of goalkeeper transfers this summer. Claudio Bravo is set to join Manchester City, with Barcelona replacing Bravo with Ajax 'keeper Cillessen, meaning Ajax have turned to Krul to replace his fellow Netherlands international.
Krul joined the Magpies as a youngster in 2005 from Dutch side ADO Den Haag and has since played 185 times for the club.
The 28-year-old also has eight caps for the Netherlands.