The 20-year-old Iceland striker bagged a hat-trick within the first half-hour to virtually make the points safe before Ahmed Musa pulled one back after 37 minutes.

But any hopes of a comeback were quickly dashed after the break. Sigthorsson was on target again in the 47th minute and rounded off the scoring after international team-mate Johann Berg Gudmundsson had helped himself to AZ's fifth.

Vitesse Arnhem were also among the goals as they came from behind to trounce Roda JC 5-2.

Marco van Ginkel netted twice with Nemanja Matic, Jordi Lopez and Haruna Babangida also finding the target as the home side produced a stylish display at Gelredome.

Mads Junker and Jimmy Hempte scored for Roda, but defeat prevented them from climbing into the top four.

The clash between De Graafschap and FC Utrecht had to be postponed due to a frozen pitch at De Vijverberg and will now be played tomorrow instead.