The 26-year-old victim, who was apparently about to enter the synagogue grounds, was hit in the head with what appeared to be a folding spade, police said. The suspect, a 29-year-old German man, was wearing military-style clothing.
The victim was given first aid at the scene by passers-by, then taken to a hospital with injuries that were described as “significant” but not life-threatening.
Officers who were on hand to protect the synagogue arrested the suspect, a police statement said. It added that the background to the assault is under investigation.
The Sueddeutsche Zeitung newspaper, which first reported on the assault, said that the victim is a Jewish student who was wearing a skullcap. Police later said that the suspect, a German with Kazakh roots, left an “extremely confused impression” and questioning him was difficult.
News agency dpa reported, without citing sources, that the suspected assailant had a piece of paper with a swastika in his pocket.
Nearly a year ago, a heavily armed white supremacist targeted a synagogue in the eastern German city of Halle on Yom Kippur, the holiest day in Judaism. He killed a passer-by and a man at a nearby kebab stall after failing to force his way into the building.
Security has since been increased at Jewish institutions across the country.
“This is not an isolated case — this is repugnant anti-Semitism and we must all stand up against it,” German Foreign Minister Heiko Maas tweeted.