IS claims it was behind murder of German teenager
The Islamic State group has claimed responsibility for a knife attack in Hamburg on 16 October which left a teenager dead and another badly injured.
IS-affiliated news agency Amaq said the group was behind the attack which left one person dead and another teenager seriously injured.
"A soldier of the Islamic State stabbed two individuals in Hamburg city on the 16th of this month," the release said, in response to "calls to target the citizens of coalition countries" that are fighting the group in Iraq and Syria.
A spokesman for Hamburg police refused to comment on the claim when contacted by AFP.
Hamburg police reported a knife attack on the banks of the Alster River earlier this month.
One victim, a 16-year-old boy, was fatally wounded, while his 15-year-old girl companion escaped unharmed.
Police launched a dragnet but never found the attacker, described as aged 23-25 and of "southern" appearance.
"The motive for the crime is unknown and the subject of further investigation," the 17 October police statement said.
News agency DPA on Sunday reported a police unit investigating political crimes was brought onto the case after the IS claim of responsibility.
The German air force is participating in the anti-IS bombing campaign in Iraq and Syria with in-air refuelling and reconnaissance flights.
Germany has so far escaped a major terrorist attack by IS along the lines of those carried out in neighbouring France and Belgium, although it has foiled several plots and suffered numerous attacks by individuals.
A teenage girl is currently on trial in Hanover after wounding a police officer with a knife in February, with prosecutors arguing IS is behind the attack.
In July, IS claimed it was behind a suicide bomb attack that wounded 15 people, as well as an axe attack in a train by a teenage asylum seeker that left five people hurt.
June saw a group of men arrested on suspicion of planning a bomb attack on western regional capital Duesseldorf, while another suspected bomb-maker was arrested in eastern Saxony in October but later killed himself in his cell.
Previously, a 41-year-old Iraqi was killed by police after wounding an officer in Berlin in September 2015.
A month before, two German jihadi fighters claiming to belong to IS in Syria released a video in which they threatened Germany and Chancellor Angela Merkel.