A man armed with a knife attacked passengers on a bus in the city of Lübeck, north of Germany, injuring several people, including one seriously, according to police.
A 34-year-old man was arrested and detained. Police said that there was no indication that the suspect had been politically radicalized.
They said on Twitter that 10 people were injured.
An area around a bus stop in the Kücknitz district was closed.
Police said that a smoking backpack was found in the bus, containing a "fire accelerator" but not explosive.
"The exact number of wounded is still unclear, there have been no deaths," police said in a statement. "The crime context is still unclear and is the subject of the ongoing investigation."
The statement adds: "The identity of the author has been clarified: a 34-year-old German citizen residing in Lubeck. At the present time no indication that the man was politically radicalized and no sign of a terrorist background. "
The attack took place at 13:47 local time (11:47 GMT). An eyewitness told the local newspaper Lübecker Nachrichten that a passenger had just yielded his seat for an elderly woman, when the attacker stabbed him in the chest.
The bus driver stopped by the side of the road and the passengers fled. Police say the suspect was under police control
In April, a man drove a van into a group of people outside a restaurant in the German city of Münster, killing two people before killing himself.
Police said that there was no connection to terrorism in this case.
In Berlin in December 2016, a Tunisian who had links with Islamist militants hijacked a truck and plowed a Christmas market, killing 12 people.