It ends a successful 12 months at the Tunisian outfit for Krol, who claimed league honours in May for the provincial outfit.
The Dutchman then steered the team to the continental title with a 3-2 aggregate win over TP Mazembe Englebert of the Democratic Republic of Congo at the weekend.
Krol also served as caretaker boss of Tunisia when they played against Cameroon in the World Cup qualifying-play off in October and November. Cameroon won the tie 4-1 on aggregate.
Krol guided Bucs to a treble in the 2010/11 season.