Heracles axe De Jonge
De Jonge had been in charge for 14 months and helped the club avoid relegation in 2013-14.
However, four defeats from four this term prompted the Heracles board to make a change.
A 3-1 loss at Excelsior on Saturday proved the final straw and Heracles have won just two of their last 16 Eredivisie games under the 51-year-old.
The international break gives senior Heracles officials time to find De Jonge's successor as the club are not in action again until September 13.
A trip to champions Ajax in a fortnight appears set to provide a stern test for the Eredivisie's bottom side.