Police charged a 20-year-old unemployed Belgian with murder after two babies and a woman were killed and 13 others wounded in a frenzied and motiveless knife attack at a creche that stunned Belgium.

Prosecutor Christian Du Four, at a news conference yesterday, identified the man only as 'Kim D', from Belsele, a village some 30 km from the scene of Friday's attack in the town of Dendermonde.

The man had no previous criminal record, Du Four said. When he was arrested he was carrying a knife, a small axe, a fake pistol and was wearing body armour, he said. Two more knives were found at the scene.

"He has not said anything, so we don't know about his motive," Du Four said. "He doesn't say anything ... he's very passive."

Local media dubbed the assailant the 'Joker' killer because his face was painted white and his eyes blackened, like the criminal mastermind in the Batman films.

He arrived at the Fabeltjesland - Fairytale Land - creche in Dendermonde, 30 km west of Brussels, in mid-morning last Friday saying he wanted to ask a question.

But he then ran into the creche's rooms and launched his attacks, slashing at victims with a knife, before cycling off.

There were 18 infants aged up to three years and six adults in the creche. Those killed were aged six and nine months and a woman child minder, aged 54.

Some of the wounded children would require plastic surgery, hospital staff said.

Belgium was in shock. De Morgen newspaper bore the headline 'Cold, Bloodthirsty, Inhuman', while the Gazet Van Antwerpen simply asked 'Why?'.