A man wielding a large kitchen knife stormed into a supermarket in the German city of Hamburg on Friday, killing one person and wounding four others before being detained by police.

“There is no valid information yet on the motive” of the man, who “entered a supermarket and suddenly began attacking customers”, said police.

German daily Bild published a picture of the attacker in the back of a police car with a white, blood-soaked bag over his head, and reported that he cried “Allahu Akbar” (God is Greatest) in the supermarket.

A female witness standing in line at the supermarket till also told NTV rolling news channel that “as he was running out… he held up his arms and shouted Allahu Akhbar .”

She said she was “afraid of dying,” as she was “queuing for the till and couldn t get away”.

A police spokeswoman said the “Allahu Akhbar” accounts could not be confirmed.

The suspect, who has not yet been identified, fled the supermarket after the attack.

But witnesses gave chase and overpowered the man, who was slightly injured.

“It was definitely a sole attacker. The first reports about a possible motive of a robbery have not been confirmed,” Hamburg police tweeted.

Police have blocked off the lively and diverse high street dotted with cafes and shops in the northeast of the port city, Germany s second largest and host of the G20 summit of world leaders in early July.

Anti-terror police have also been deployed to the scene, according to Bild.

Homicide investigators are leading the probe, said police, adding that they were pursuing “all leads” for a motive.

There was no information immediately available about the dead person. Police said that one of the four injured was in a serious condition.