Five people were injured, two seriously, after a stabbing incident in Amsterdam's city center on Thursday.

Witnesses said the suspect stabbed a number of people at random on Sint Nicolaasstraat, near Dam Square.

"Among the victims are a 67-year-old woman and a 69-year-old man, both American nationals; a 26-year-old man from Poland; a 73-year-old woman from Belgium; and a 19-year-old woman from Amsterdam," Dutch police said. 

The suspect was detained, police added, describing him as young man with short blonde hair.  

Bystander overpowered perpetrator

One witness told Dutch media that the attacker had stabbed a young woman in the back, with the perpetrator then running away. 

"I saw a knife at least 10 centimeters (nearly four inches) sticking out of the girl's back, between her shoulders," they told Amsterdam newspaper Het Parool. 

Dutch authorities said a bystander overpowered the suspect during the attack, with the alleged perpetrator taken to the hospital because of "an injury to his leg." 

Amsterdam police had said a motive is unclear and an investigation had been opened into the attack. 

The police had closed off the area where the attack occurred, but later reopened it. 

Amsterdam police ask footage

Emergency responders rushed to the scene of the attack to help victims.

At lease one of the victims is understood to have been put on a stretcher and was then boarded into an ambulance.     

Amsterdam police have asked those who witnessed the attack to share any footage of the incident with authorities.

"The police investigation is in full swing and is currently the highest priority," Amsterdam Mayor Femke Halsema said in a statement.

"We hope to gain clarity soon about the background of this horrific stabbing incident," she added. "Our hearts go out to the victims, their families and their loved ones."  

Edited by: Zac Crellin