A speeding car hurtled towards an open top bus carrying the Queen of the Netherlands today before smashing into a crowd and killing four people who were watching the royal parade.
A 38-year-old Dutchman, who was driving a black hatchback, has been arrested on suspicion of carrying out an attack on the Royal Family.
Thirteen people were injured, five of whom remain in a serious condition, but the Queen and fellow members of the Dutch royal family were not hurt.
The black Suzuki ploughed through the crowd during a parade to mark the Queen's Day national holiday in the city of Apeldoorn.
Princess Maxima, wife of heir Willem-Alexander, watched in horror, with her hand over her mouth, as the vehicle sped a few metres past the royal bus.
Footage of the incident shows the damaged car continuing to be driven at high-speed after crashing into members of the crowd.
People were thrown up into the air as the car swerved across police railings, where hundreds were waiting to see the Queen. The car was only halted once it had slammed into a stone monument in the centre of the city, about 50 miles east of Amsterdam.
Queen Beatrix responded to the attack in a national broadcast this afternoon. "What started as a beautiful day has ended in terrible drama, which has shocked us deeply," she said.
A spokesman from the Dutch prosecutor's office said the suspect was believed to have purposely targeted the Royal Family.
"We have reason to believe that this was a deliberate act," said Ludo Goossens, a public prosecutor. He said there were no indications of terrorist links nor were there signs of explosives.
Mr Goossens said the police suspected that the attack was deliberate "based on initial contact with the suspect before he was freed from the car".
Video showed at least one victim receiving emergency resuscitation in the road while paramedics were attempting to save the lives of several others who had been hurled to the tarmac.
A policeman narrowly escaped injury when he jumped off his bicycle to avoid being caught between the car and railings in front of the monument.
Peter von de Vorst, a witness, said that the incident was like watching a Hollywood film. "It was a really nice day. Then you hear a bang. Everyone looks up and you see people indeed flying through the air," he said. "This must be a joke or a strange prank. Then suddenly panic and you realise that something really terrible has happened."
It was not clear how the car managed enter the parade area, which police had sealed off hours before.
Police officers arrested the suspect, who was slumped against his seat with blood on his forehead, and put him into an ambulance
Shortly after the incident, investigators and a sniffer dog examined the car for explosives, then sawed off the roof of the car for a further inspection.
Fred de Graaf, the Mayor of Apeldoorn, said all festivities were cancelled. "The scare and the images that the family has seen are reason to break off the official programme," he said. Holiday programmes were also called off in the port city of Rotterdam, and more were likely to be cancelled around the country.
Hundreds of thousands of people gathered in the main Dutch cities last night and today to celebrate the national holiday. The royal family normally spends the day in a small Dutch community.
