Amsterdam  - The Dutch royal family was the real target of a car that ploughed into spectators, killing four, at a parade in the city of Apeldoorn on Thursday, Dutch officials reported.

Speaking at a press conference, officials said the 38-year-old driver of the car confessed to attempting to ram the open-top bus carrying the 71-year-old queen as well as Crown Prince Willem- Alexander and his wife Maxima during Queen's Day celebrations, a national holiday in the Netherlands.

The black Suzuki Swift missed the bus after smashing through barriers, hitting several people and dragging some along the road with it. The car then crashed into a monument nearby.

In addition to the dead, five people were seriously injured and another eight suffered minor injuries in the incident in Apeldoorn, the town's mayor Freed de Graaf told an earlier press conference.

No explosives were found in the car, the police spokesman said.

The driver, who sustained serious injuries, was removed from the wreckage of the car by firefighters and later underwent surgery. He was last reported in critical condition.

The man had no history of mental health problems, the police said.

Queen Beatrix expressed her "deepest sympathy" for the dead and the survivors. She cancelled a ceremonial march-past scheduled in memory of her mother, Queen Juliana, who died in 2004.

Prime Minister Jan-Peter Balkenende said it was "a sad day for the Netherlands."