At least 14 people have been injured after a 34-year-old man attacked passengers with a knife on a packed bus in the northern German city of Luebeck.

Police said the man was overpowered and taken into custody after the  attack on Saturday (Friday 1.47pm local time).

Sources told the local Luebecker Nachrichten newspaper the Iranian-born attacker had German nationality and had lived in Luebeck for years.

Schleswig-Holstein state police said: “There was an incident on a bus in Lübeck kücknitz. People were injured. No one was killed. The perpetrator was overpowered and is now in police custody”.

In a series of Twitter updates overnight, police said there was no evidence of the attack being terror-related.

“The identity of the offender is clarified … a 34-year-old German citizen residing in #Lübeck”.

“There are currently no indications of a political radicalisation … no signs of a terrorist background whatsoever,” it read.

“We ask for your understanding that we cannot provide any information about the identity of the suspect at the moment.”

“It is important to us to only disclose reliable information in order not to fuel speculation and not to obstruct the investigation.”

Eyewitnesses told local media several passengers were stabbed with what appeared to be a kitchen knife, others were punched and some were injured as the bus came to a stop. Photo: AAP

The packed bus was heading in the direction of Travemünde, a popular beach close to Lübeck.

The bus driver immediately stopped the bus, allowing passengers to run to safety.

The Luebecker Nachrichten quoted a witness as saying: “One of the victims had just given up his place to an older woman when the attacker stabbed him in the chest.”

The paper said local residents heard loud screams “like two people slaughtering each other” when they ran out to see the bus driver injured.

Prosecutors later said the man, who eye witnesses said was wearing dark sunglasses and a jacked during the attack, was refusing to speak with investigators.

“The background to the crime is still unclear and the subject of the ongoing investigation,”

The paper reported at least 14 people were wounded, two seriously.

In April, a man drove a camper van into a group of people sitting outside a restaurant in the German city of Muenster, killing two people before shooting himself dead, Reuters reported.

There was no evidence of any link to Islamist militancy and he was not a refugee.

In Berlin in December 2016, a Tunisian whose request for asylum was turned down and who had links to Islamist militants hijacked a truck and ploughed into a crowded marketplace. Twelve people, including the man driving the truck when it was hijacked, were killed, Reuters reported.

-with agencies