The assailant, a German citizen, was imprisoned after trying to join the Islamic State but freed weeks before attacking a gay Pride event in Berlin.
One person has died
Police asked for information about the whereabouts of a 21-year-old man.
A search is underway for one or two suspects, according to Berlin police.
Police a said a car had hit several people in a park near the pride march route.
Russian officials say an unidentified assailant has detonated an explosive device next to a patrol vehicle in Moscow, killing himself and a police officer and leaving two other officers injured