People flew through the air after the car swerved across police railings, where the crowd was lined up five or six deep to see the immensely popular royal family pass on its way to the Het Loo palace on the Queen's Day national holiday.
Prosecutors said they believe the incident was deliberate, but not an act of terrorism. They did not indicate a motive or say why the queen might have been a target. The driver was a 38-year-old white Dutch male with no police record or history of mental illness, police said. They would not give his name.
It was not clear how the car managed to enter the parade area, which police had sealed off hours before.
Police officers removed the injured driver, who was slumped against his seat with blood on his forehead, from the vehicle and put him into an ambulance. Other officers gave medical aid to spectators before they were taken to the hospital.
"From initial contact with police before the suspect was removed from the car ... we have reason to believe it was a deliberate action," prosecutor Ludo Goossens told reporters.
Apeldoorn Mayor Fred de Graaf said eight of the injured were in serious condition.
"What began as a great day has ended in a terrible tragedy that has shocked us all deeply," a visibly upset Queen Beatrix said in a brief statement broadcast on national television channels.
"We are speechless that something so terrible could have happened. My family, and I think everybody in the country, sympathize with the victims, their families and friends and all who have been hit so hard by this accident," she said.
Shortly after the incident, investigators and a sniffer dog examined the car for explosives, then sawed off the roof of the car for a closer inspection. Dutch television footage showed Crown Prince Willem-Alexander and his wife, Princess Maxima, standing at their seats in the bus's high open platform and watching with surprise. Maxima held her hand over her mouth in apparent horror.
The bus was not hit and no one in the queen's entourage was injured.
A policeman narrowly escaped injury when he jumped off his bicycle to avoid being hit.
De Graaf said all festivities were being canceled. Holiday programs also were called off in the port city of Rotterdam, and more were likely to be canceled around the country.
Journalist Peter von de Vorst told RTL television that the incident was like watching a horrible movie.
"It was a really nice day. Then you hear a bang. Everyone looks up and you see people indeed flying through the air. This must be a joke or a strange prank. Then suddenly panic, and you realize that something really terrible has happened," he said.
Hundreds of thousands of people flocked to the main Dutch cities on Wednesday night and Thursday to celebrate the national holiday, originally intended to celebrate the birthday of Beatrix's mother Queen Juliana.
The royal family normally spends the day in a small Dutch community.
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