Four people were killed today when a car ploughed into spectators in what police described as a deliberate attack on a parade attended by Queen Beatrix of the Netherlands, dpa reported. Five people were seriously injured and another eight suffered minor injuries in the incident in Apeldoorn, the town's mayor Freed de Graaf told a press conference. A police spokesperson confirmed that the attack had been deliberate but was unable to say what the motive was. Investigators ruled out a terrorist attack. No explosives were found in the car, the police spokesperson said. The incident was shown on television as a black Suzuki Swift smashed through barriers, hitting several people and dragging some along the road with it. It then crashed into a monument close to an open-top bus carrying the 71-year-old queen as well as Crown Prince Willem-Alexander and his wife Maxima. The royals were attending Queen's Day celebrations, a national holiday in the Netherlands. "It's a bloodbath. Terrible," said a woman in a television interview. "It could only be an attack," a man added. The driver of the car survived the crash but sustained serious injuries. Firefighters removed him from the wreckage of the car. He later underwent surgery. The 38-year-old has no history of mental health problems, the police said. Officers meanwhile took immediate action to ensure the safety of the royal family. 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."