Eleven other children and two other women workers were wounded and being treated at local hospitals, authorities said. Three of the children were in a critical condition.
The assailant arrived at the creche at around 10 a.m. (0900 GMT) saying he wanted to ask a question, but then leapt into one of the rooms to launch his attack before stabbing more victims in another room.
The man cycled away before being arrested at around 11.30 a.m.
The creche, in the town of Dendermonde, 30 km (20 miles) west of Brussels, held 18 children aged up to 3 years and 6 adults at the time.
Belgian media said that the man in his 30s was a psychiatric patient, but authorities did not confirm this, saying only that he would appear before a magistrate later on Friday.
"Many parents are in shock," Interior Minister Guido De Padt told a news conference.
Hospitals had made photos of the wounded available to concerned parents to help them find their children.
Last Mod: 23 Ocak 2009, 15:30