The axe attack on a German train on Monday evening was carried out by an individual perpetrator who "felt goaded" by the propaganda of the Islamic State (IS), said German Interior Minister Thomas de Maiziere on Wednesday.
A video, which was released by the IS on the Internet claiming responsibility for the axe attack, does not contain any evidence of an arrangement with the IS, according to de Maiziere.
The 17-year-old refugee Riaz Khan Ahmadzai injured five people near Wuerzburg in the southern German state of Bavaria with a knife and an axe. Most of the victims were Chinese tourists, among whom two were critically wounded.
"It is perhaps a case which lies on the border between rampage and terror," De Maiziere said in Berlin.
He condemned the act as a "brutal act of indiscriminate violence," saying that "the background of the act must be further clarified."
Meanwhile, he also called for more video surveillance, more police, and better protection of police officers.
German media Spiegel Online reported police had found a "hand-painted IS flag" in the room of the 17-year-old Afghan.