A panic broke out at a Dutch war memorial service in central Amsterdam, setting off a stampede that injured at least 30 people and prompted bodyguards to evacuate the royal family.
The incident came just over one year after an assassination attempt against Queen Beatrix.
A man began to yell during a moment of silence during the annual service to memorialise the nation's war dead. Someone then reportedly discovered a suspicious suitcase, and several people were trampled in the resulting panic. Two people have been arrested in conjunction with the incident, police said.
The royal family later returned to the scene, and the ceremony was completed without further incident.
Queen Beatrix, Crown Prince Willem-Alexander and his wife, Princess Maxima, later visited some of the injured.
During a celebration of Queen's Day April 30, 2009, a 38-year-old man drove his vehicle into a procession, aiming at the bus in which the royal family were riding. He died after crashing his car into a monument near the bus.
The scare prompted tightened security at public events involving the royal family.