Alkmaar see off amateurs after extra time
Thijs Houwing opened the scoring for Spakenburg after six minutes but second-half goals from Pontus Wernbloom and Stijn Schaars seemed to put Alkmaar back on track.
The amateurs did not give up, however, and a last-minute equaliser from Christy Bonevacia sent the match into extra time. Alkmaar's blushes were spared as Wernbloom, Jonathas and Mounir El Hamdaoui scored to make it 5-2.
In an all top-flight encounter, Stanislav Manolev and Jonathan Reis were on target to earn PSV Eindhoven a 2-0 victory at Roda JC Kerkrade.
Manolev opened the scoring in the first half after a defence-splitting combination with Ibrahim Afellay, while Reis volleyed home a cross from Balazs Dzsudzsak after the break.
Holders Heerenveen beat second division side RBC Roosendaal 4-2, while Luuk de Jong struck twice as last year's finalists Twente Enschede beat amateurs Capelle 3-0.
Groningen hammered hosts Vitesse Arnhem 5-1.
On Tuesday Feyenoord beat Den Bosch 2-0 to reach the last 16. Ajax Amsterdam will be in action on Thursday when they travel to second division Dordrecht.