Barcelona have accused police of using “disproportionate” force against their fans before Sunday’s 5-0 win at Elche.
Videos have emerged on social media appearing to show confrontations between police and fans as they queued to enter the Estadio Martinez Valero in Elche, Alicante.
Barcelona say the use of force to detain one supporter “lacked the necessary justification and appropriateness”.
A statement said: “FC Barcelona condemns the disproportionate use of force against club members and fans during the incidents that took place yesterday in the vicinity of the Martinez Valero stadium ahead of the league game against Elche.
“In particular, the club considers that the procedure used to detain one of our fans was disproportionate and that the use of force lacked the necessary justification and appropriateness.
“FC Barcelona has made itself available to the detained fan and his family to offer them any support they may require.”
Barcelona also accused police of confiscating Estelada flags from fans, which are used by supporters of Catalan independence and often waved by Barca fans.
“The Estelada is a legally endorsed symbol and its display constitutes a legitimate exercise of freedom of expression. As such, it cannot in itself be considered an incitement to hatred or violence,” Barcelona said.
Raphinha and Fermin Lopez both scored twice in Barcelona’s victory.
BBC Sport has contacted local police and the regional government for comment.