The family say they do not know of any threats against them, and someone must have made a mistake. The police are also baffled. "They are a completely normal family, with jobs and so on," says police spokesman Mats Attin.
According to the police the father woke up about a quarter to four am when a concrete brick was thrown through the ground-floor flat's kitchen window. "When he approached the broken window the hand grenade was thrown in." The device passed him and hit the bedroom door, which he had luckily already closed, and the grenade bounced off into the hallway.
Officer Attin says the children are alive thanks to the concrete walls which protected them, and the father is suffering only light injuries from the blast wave, since there was a load-bearing wall between him and the explosion.
"It looks like a Swiss cheese in there. There's a crater in the floor," says Mats Attin to news agency TT.
The apartment is in Seved, an area of Malmö that has a crime problem. Police guess the attack was intended for someone else.
The family has been moved to a safe location, says police spokeswoman Marie Persson to Swedish Radio Malmö.