Four people were wounded by a man wielding a knife at a station east of Munich and police are investigating a possible Islamist connection.
The man attacked passers-by shortly before 5am (local time) on Tuesday at Grafing station. One victim was said to be in a life-threatening condition.
The attacker was eventually overpowered by police. A man has been arrested.
Some witnesses said he shouted "Allahu akbar" ("God is great" in Arabic) but the motive for the attack is unclear.
Bavarian public radio reports that the Munich prosecutor has imposed a news blackout and that contradictory statements have emerged from the scene.
Grafing mayor Angelika Obermayr told Sueddeutsche Zeitung that the suspect was a German national.
"The idea that people get on an S-Bahn train on a beautiful morning or do their paper round and then become victims of a maniac is terrible," she was quoted as saying.
One of the platforms at Grafing station has been cordoned off and commuter trains have been hit by delays.
-BBC
