Barcelona transferred Emre Demir from Turkey's Yukatel Kayserispor for 2 million euros ($2.34 million) plus bonuses, the Catalan club said in a statement on Thursday.
The 17-year-old will stay at the club until 2027, and his release fee has been set at 400 million euros, according to the press release.
Yukatel Kayserispor also confirmed the transfer on Twitter, saying Demir will put on the Barcelona jersey starting next season, according to the agreement and UEFA rules.
Demir, a Kayserispor youth team product, is an attacking midfielder but can also play as a winger. He is the youngest goal scorer in Turkish Süper Lig history at 15 years, nine months and 25 days.
Barcelona is having a difficult period as it collected only nine points in five games in La Liga. The club's manager Ronald Koeman is under growing pressure following a slow start to the campaign that has seen Barca drop points to Athletic Bilbao, Granada and Cadiz in their opening five La Liga games, while also losing 3-0 to Bayern Munich in the Champions League.
Amid reports Barca is lining up replacements for Koeman, with Belgium boss Roberto Martinez supposedly among the candidates, Koeman refused to answer any questions from reporters at Wednesday's news conference.