German media reported that over 10 people were feared dead in a shooting in a shopping mall in the southern city of Munich.
TV images showed dozens of emergency vehicles outside the mall.
The shopping center is next to the Munich Olympic stadium, where the Palestinian militant group Black September took 11 Israeli athletes hostage and eventually killed them during the 1972 Olympic Games.
Friday's attack took place a week after a 17-year-old asylum-seeker wounded passengers on a German train in an axe rampage claimed by Islamic State. Bavarian police shot dead the teenager after he wounded four people from Hong Kong on the train and injured a local resident while fleeing.
German Justice Minister Heiko Maas told Bild newspaper's Friday edition that there was "no reason to panic but it's clear that Germany remains a possible target".
The incidents in Germany follow an attack in Nice, France, on Bastille Day in which a Tunisian drove a truck into crowds, killing 84. Islamic State also claimed responsibility for that attack.