A 15-year-old footballer from Berlin died Wednesday after he was seriously injured in a fight with players from a French team at an international youth tournament, police said.
The teenager "died in hospital as a result of his severe brain injuries" after being hit on the head in the altercation in Frankfurt on Sunday, local police said in a statement.
A 16-year-old player from the French team was arrested following the fight and was still being held in custody, police said.
The brawl occurred following the final whistle in a game between the victim's side JFC Berlin and a team from French second-division club Metz.
Investigators were still looking at the "detailed sequence of events" that led to the player's injuries, they said.
The victim was seemingly hit "on the head or neck" before he "fell to the floor and had to be resuscitated", police said in a separate statement Tuesday.
The victim, already declared brain dead on Tuesday, was kept on life support so his organs could be donated, a spokeswoman for the Frankfurt prosecutor's office said.
Metz released a statement on Wednesday evening.
"Following the tragedy that occurred this weekend in Frankfurt, FC Metz has learned through the media of the death of the young opposing player today," it said.
"The whole of FC Metz is deeply shocked by this tragedy and sends its most sincere condolences to the family and loved ones of the young player."
The statement added that the club "would once again like to remind everyone that FC Metz Performance Program, as well as all the players and parents present, are of course at the disposal of the German authorities to help with the investigation".
On Tuesday, the club had confirmed that a player from its "Performance Programme", which gives "young footballers... from all over the world access to a high-level training structure", was being held by German authorities.
The suspected attacker "denies having deliberately caused serious bodily harm", the club said.
The tournament organisers also said Tuesday that they were shocked by the events, describing them as "unbelievably sad".