A 17-year-old Afghan asylum seeker shouted “Allahu akbar” (“God is great”) during an axe and knife attack on a train in southern Germany that injured at least five people, a German top security official said.

Bavaria’s interior minister Joachim Herrmann said on public television that investigators raiding his room also found a hand-painted flag of the Islamic State group.

The attacker was shot and killed by a special police unit which coincidentally happened to be nearby.

“Even during the first emergency call, a witness said that the attacker was shouting ‘Allahu akbar’ on the train,” Herrmann told ZDF Television.

“Also, during the search of his room, a hand-painted IS flag was found.”

Herrmann said that it was still too early to draw conclusions about the attacker’s motive.

Police stand by the regional train on which a man allegedly wielding an axe attacked passengers.

The attacker, who was not identified by the authorities, came to Germany two years ago as an unaccompanied minor, and applied for asylum in March of last year.

He lived in a home for young refugees until two weeks ago when he was placed with a foster family in the Wuerzburg area. Investigators were talking to the foster family, witnesses and the attacker’s friends.

The attacker injured at least four people on the train near Wuerzburg-Heidingsfeld on Monday night, and also a woman outside the train as he fled.

Witnesses said the interior of the train was covered with blood and looked “like a slaughterhouse”, the German news agency dpa reported. About 30 passengers were on the train at the time; more than a dozen were treated for shock.

Herrmann said at least two victims – members of a Chinese tourist family – are still in critical condition.

German officials did not identify the victims, but Hong Kong’s immigration department said on Tuesday that among those injured in the attack were four members of a family of five from the southern Chinese city.