A man armed with a knife attacked people on a bus in the northern German city of Luebeck on Friday, wounding at least 14 people, two seriously, before being arrested by police, the local newspaper reported.
Schleswig-Holstein police said no one was killed in the incident and confirmed the suspect was in custody. They did not immediately give further details.
"The offender was overpowered and is in police custody. We are still at the site and will continue to report from here," the police said on Twitter.
The Luebecker Nachrichten newspaper cited state prosecutor Ulla Hingst as saying: "Nothing can be ruled out, including a terrorist background."
Hingst told national newspaper Bild the attack took place at 1.47 pm local time.
Luebecker Nachrichten, which said the attacker appeared to be in his mid-30s, 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."
An area around a bus stop in the Luebeck neighbourhood of Kuecknitz was sealed off by police, spokesman Dierk Duerbook told Bild.
Earlier, police in Schleswig-Holstein, the state where Luebeck is located, tweeted that there was a major police deployment under way in the city.
Luebeck police did not respond to repeated calls for comment.
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. 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.
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