Dutch police are looking for witnesses to a knife attack in Rotterdam that left one person dead and another seriously injured.

THE HAGUE – Dutch police appealed for help from witnesses on Friday in connection with an investigation into a stabbing attack in which one man was killed and another seriously injured in the port city of Rotterdam.

The suspect was arrested after being restrained by members of the public and police on Thursday evening. There was no immediate information on a motive for the attack, but police said Thursday evening that witnesses reported the attacker shouting “Allahu akbar,” an Arabic phrase meaning God is great.

“This is part of the investigation,” police spokesman Wessel Stolle said on Wednesday evening.

Police said in a statement that a 32-year-old man from Rotterdam was killed and a 33-year-old man from Switzerland was seriously injured in a stabbing attack near the historic Erasmus Bridge. The suspect is a 22-year-old man from the central Dutch city of Amersfoort, who reportedly attacked his victims with two large knives.

Police have not released the identities of the suspect or the victims of the stabbing, in line with Dutch privacy guidelines.

Sports instructor Reniël Renato David Litecia said he hit the attacker with two sticks after seeing him attack someone, then managed to take the knives and throw them away.

He said he initially thought it was a fight, “but when I started running in that direction, I saw it wasn’t a fight. It was a man with two long knives stabbing another young boy, and when I started screaming, he turned around and started going at whoever was around him.”

Another police spokeswoman, Kristel Arntz, said the attacker most likely attacked one person in an underground car park and then a second victim near a busy terrace at one end of a bridge over the Neue Maas river, which flows through Rotterdam.

Arntz added that the investigation was still too early to determine a motive.

“We have arrested a suspect, we will question him. We will look at all witness statements and then check what the possible motive was,” she said.