A knife-wielding man described as a stateless Palestinian has fatally stabbed two people and injured seven others on a train in northern Germany before being grabbed by passengers and arrested by police, officials said. The motive of Wednesday's attack was not immediately known.

Three people were severely injured and four others suffered minor injuries.

The attacker was also injured and taken to the hospital, police said.

The spokesman said the investigation into a motive was focused on "all directions" including possible extremism or psychological problems on the part of the assailant.

No details were given about the identity of the victims.

German interior minister Nancy Faeser expressed shock about the brutal attack.

“The knife attack in a regional train is shocking news. All our thoughts are with the victims of this terrible act and their families,” she said.

The interior minister of Schleswig-Holstein state, Sabine Suetterlin-Waack, condemned the attack.

“It is terrible,” Suetterlin-Waack told German public broadcaster NDR. “We are shocked and horrified that something like this has happened.”

Train operator Deutsche Bahn expressed its condolences on Wednesday evening, saying that “our deepest sympathy goes to the relatives of the victims. We wish those injured a speedy and complete recovery”.

Germany has been hit by several deadly knife attacks in recent years, some carried out by extremists and others by people suffering serious psychological problems.

A Syrian jihadist was given a life sentence in May 2021 for stabbing a German man to death and severely wounding his partner in a homophobic attack in the eastern city of Dresden.

Last June a 30-year-old woman died from her injuries after an apparently random knife attack on students at a university campus.

In September 2022, a knife-wielding man wounded two people in Ansbach, a Bavarian town close to Nuremberg, before being fatally shot by police who said they were investigating a possible "Islamist or terrorist context".

In December 2022, an asylum seeker from Eritrea killed a 14-year-old girl and seriously injured another, aged 13.

A German court in December sentenced a Syrian-born Islamist to 14 years in prison for a knife attack on a train in which he injured four passengers.

Last year, a German court committed a Somali to a psychiatric hospital after he stabbed three people to death in the southern city of Wuerzburg in 2021.