Police said people had been killed and injured and that an attacker had been shot, but did not give details.
The situation was now under control, police said.
A reporter for ARD public television said he had been told by police that there were no indications of a terrorist motive behind the attack.
“The attacker was overpowered after police used a firearm,” Lower Franconia police said on Twitter. “There are no indications of a second suspect. There is NO danger to the population.”
Videos posted on social media showed a young man seemingly holding a knife being warded off by other men holding chairs until police arrived. Another video appeared to show blood on the ground.
The videos matched the reported location of the attacks on and around Wuerzburg’s central Barbarossaplatz, though it was not immediately possible to confirm when they had been made.
Wuerzburg is a city of some 130,000 people south-east of Frankfurt.