The teen is seen threatening further attacks by the Islamic State
Islamic State's propaganda wing has released a video of a teenage Afghan refugee who attacked train passengers with an axe and a knife in Germany.
The footage from Amaq News Agency is just over two minutes long and shows the boy, who is named as Muhammad Riyad, identify himself as a "soldier of the Caliphate".
Holding a knife in his right hand, he says in Pashto he will carry out an "operation" in Germany.
He goes on to threaten further attacks by IS "in every village, city and airport", according to a report by the non-governmental counter terrorism organisation SITE Intelligence Group.
The footage was released hours after IS claimed the attacker was one of its fighters.
The 17-year-old, who is reported to have had a handmade IS flag at home, was shot dead by police as he tried to flee the scene after injuring at least four people on a train outside the city of Wuerzburg.
Some witnesses had heard the suspect shout "Allahu Akbar" (God Is Great) during the assault.
Three of the victims were seriously wounded, while another suffered minor injuries, police said.
An eyewitness who lives next to the railway station told DPA news agency the train carriage, which had been carrying around 25 people, looked "like a slaughterhouse" with blood covering the floor and seats.
The man, who declined to give his name, said he saw people crawl from the carriage and ask for a first-aid kit as other victims lay on the floor inside.
Another witness told German newspaper Bild that they had never seen "so much blood" before.
Among the injured were four members of a family from Hong Kong, according to the South China Morning Post.
They are a 62-year-old man, 58-year-old woman, their 27-year-old daughter and her 31-year-old boyfriend, the paper said.
Another 14 people were being treated for shock.
It is understood the attacker made his way to Germany as an unaccompanied minor and had at first lived in a shelter before moving in with a foster family in the nearby Bavarian town of Ochsenfurt.
Joachim Herrmann, the interior minister of Bavaria state, said officials were still investigating the motive for the attack.
"In the meantime, a text in Pashto was also found that was partly written in Arabic characters and partly in Latin characters, which indicates that this could be someone who has self-radicalised recently," he said.
The attack took place between Ochsenfurt and Wuerzburg-Heidingsfeld train stations in Bavaria at around 9.15pm local time on Monday.
More than one million migrants entered Germany last year, including more than 150,000 Afghans.
It is unclear whether the suspect was among them or had already been living in the country for some time.