Islamic State has claimed responsibility for a knife attack on a young couple in Hamburg, which claimed the life of a teenager and left his girlfriend injured.

The incident, which was not widely reported, happened late in the evening of October 16 when the victim, 16, and his girlfriend, 15, were sitting down beneath the Kennedy Bridge in the Germany port city. The suspect remains at large and his identity is unknown.

News of the stabbing comes just a day after four people were stabbed at a railway station in Frankfurt, although the motive behind the attack remains unclear.

ISIS has claimed responsibility for the fatal stabbing of a 16-year-old boy beneath Kennedy Bridge in Hamburg prompting fears he is the first victim of the terror group on German soil

According to police investigating the stabbing in Hamburg, a man approached the couple from behind and suddenly stabbed the boy - identified only as Victor by police - several times. The attacker then pushed the girl into the Outer Alster Lake before fleeing.

The girl managed to escape from the water and alert emergency services, but Victor died a short time later in a city clinic from multiple stab wounds.

On Saturday, the ISIS news agency Amaq claimed responsibility for the murder.

'A soldier of the Islamic State stabbed two individuals in Hamburg on the 16th of this month. He carried out the operation in response to calls to target the citizens of coalition countries,' Amaq said in a statement.

If true, the killing would be the first lethal attack carried out by the terror group on German soil.

Tributes have been left at the scene by those who knew the victim.

'Victor - we miss you', reads one, while another tribute is written on a banner: 'Our beloved friend, we think of you and miss you.'

An Afghan refugee who pledged allegiance to the terror group attacked passengers on a train with an axe in July and was killed by police, but his victims survived.

A sign reading, 'Victor - we miss you', has been placed at the site of the stabbing in Hamburg

Another tribute to Victor on a banner reads: 'Our beloved friend, we think of you and miss you'

People walk past a memorial to the 16-year-old victim, who was stabbed earlier this month

A week later, a suicide bomber killed himself with a home-made bomb outside a cafe in Ansbach, injuring 19 people, with no fatalities.

Hamburg police said they are looking for a man of 'southern' appearance, is estimated between 23 to 25-years-old and 5ft 9in to 6ft 2in tall. He has stubble and short, dark hair.

The authorities have not commented on the possible terrorist link.

It remains unclear whether four people stabbed at a Frankfurt railway station on Saturday were targeted as the result of a random attack or an Islamic radical.