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 Luebecker Nachrichten newspaper reported.
Schleswig-Holstein police said no one was killed in the incident and confirmed that 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 continue to will report from here," the police said on Twitter.
Luebecker Nachrichten cited state prosecutor Ulla Hingst as saying: "Nothing can be ruled out, including a terrorist background."
The paper, 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 newspaper.
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 immediately respond to repeated calls for comment.