At least 14 people have reportedly been wounded, two of them seriously, in a knife attack on a bus in Germany.

A suspect - believed to be in his mid-30s - was arrested after the stabbings in the northern city of Luebeck on Friday afternoon. The motive is unclear.

The packed bus was heading in the direction of Travemuende, a popular beach, when a man pulled a weapon on passengers, according to local media.

The bus driver immediately stopped the vehicle, allowing passengers to escape, local newspaper Luebecker Nachrichten reported.

A police crew that happened to be nearby was able to get to the scene quickly, allowing officers to detain the suspect.