The packed bus was heading in the direction of Travemünde, a popular beach close to the city of Lübeck, when a man pulled a weapon on passengers, local media Lübecker Nachrichten reported, quoting an unnamed witness.
The bus driver immediately stopped the vehicle, allowing passengers to escape, the daily said on its website.
“The passengers jumped out of the bus and were screaming. It was terrible. Then the injured were brought out. The perpetrator had a kitchen knife,” a witness who lives close to the scene, Lothar H., told the daily.
An unnamed female passenger on the bus said one of those injured had only just given up his seat to an elderly woman, “when the perpetrator stabbed him in the chest.”
A police car which happened to be close by was able to get to the scene quickly, allowing officers to detain the perpetrator, added the report.
The suspect, a 34-year-old German national born in Iran, appeared before a magistrate on Saturday. His motives remain unclear.
Police investigating the case believe the man doesn’t have a terrorist background according to current intel, said Schleswig-Holstein Interior Minister Hans-Joachim Grote (CDU) on Friday.
Police quoted by national news agency DPA said there were no fatalities. By 4 p.m. Friday, the assailant had been detained, according to police.
“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,” said police from the state of Schleswig-Holstein on Twitter.
Es hat in #lübeck #kücknitz einen Vorfall in einem Linienbus gegeben. Dabei wurden Menschen verletzt. Es wurde niemand getötet. Der Täter konnte überwältigt werden und befindet sich in Polizeigewahrsam. Wir sind weiterhin vor Ort und berichten auch hier weiter.
— Polizei SH (@SH_Polizei) July 20, 2018
While neither the motive nor full identity of the perpetrator have been established, Germany has been on high alert after several deadly Islamist extremist attacks.
Confirming that a man went at fellow passengers on the bus with a knife, Lübeck chief prosecutor Ursula Hingst added: “We will not release information on the identity of the man nor the motive of the act.”
Hingst said the man is a 34-year-old German national but that he may have been born elsewhere.
The prosecutor meanwhile added that “the background (of the attack) is unclear, we are investigating in all directions, we can not rule anything out at the moment.”
Jihadist attack risk
Germany had long warned of the threat of more violence after several attacks claimed by the Islamic State jihadist group, the bloodiest of which was a truck rampage through a Berlin Christmas market in December 2016 that left 12 people dead.
The attacker, Tunisian asylum seeker Anis Amri, hijacked a truck and murdered its Polish driver before killing another 11 people and wounding dozens more by ploughing the heavy vehicle through the festive market in central Berlin.
He was shot dead by Italian police in Milan four days later while on the run.
Germany has since been targeted again in attacks with radical Islamist motives.
In July 2017, a 26-year-old Palestinian asylum seeker wielding a knife stormed into a supermarket in the northern port city of Hamburg, killing one person and wounding six others before being detained by passers-by.
German prosecutors said the man likely had a “radical Islamist” motive.
The IS also claimed responsibility for a number of attacks in 2016, including the murder of a teenager in Hamburg, a suicide bombing in the southern city of Ansbach that wounded 15, and an axe attack on a train in Bavaria that left five injured.
In June 2018, German police said they foiled what would have been the first biological attack with the arrest of a Tunisian suspected jihadist in possession of the deal poison ricin and bomb-making material.
Germany remains a target for jihadist groups, in particular because of its involvement in the coalition fighting IS in Iraq and Syria, and its deployment in Afghanistan since 2001.
Germany's security services estimate there are around 11,000 Islamic radicals in Germany, some 980 who are deemed particularly dangerous and capable of using violence. A hundred and fifty of these potentially dangerous individuals have been detained for various offences.
Chancellor Angela Merkel has allowed in more than one million asylum seekers since 2015 — a decision that has driven the rise of the far-right
Alternative for Germany (AfD) party, which charges that the influx spells a heightened security risk.