Four people were stabbed Saturday in an attack inside the Hauptwache rail and subway station in downtown Frankfurt, German police said.
Frankfurt police confirmed via Twitter that all four victims had been taken to the hospital with stab wounds, without giving further details of their condition.
Police were investigating how many people were involved in the stabbing. The motive for the attack was not clear, officials said.
Germany was struck by a series of attacks this summer. The Islamic State group claimed responsibility for two attacks in late July, one on a train near Wurzburg and another at a music festival in Ansbach that wounded 20 people. Police fatally shot the assailants in both incidents.
Two other attacks, including a deadly mall shooting in Munich, were unrelated to Islamic extremism, according to police.