Barcelona mayor Ada Colau has expressed disapproval over Espanyol fans for waving an offensive banner about pop superstar Shakira, defender Gerard Piqué's partner, in Barcelona's 2-0 Copa del Rey win this week.

La Liga's Espanyol is facing sanctions from Spain's anti-violence commission for the derogatory act, SuperSport reported. Aside from Shakira, Espanyol supporters also displayed offensive remarks against Barca players Lionel Messi and Luis Suárez.

Piqué mocked Espanyol fans' "marvelous minority" moniker after the two teams' round of 16 first-leg tie at Camp Nou, adding that he wonders whether the group could fill their stadium for the return game, according to ESPN FC.

During Wednesday's second leg, Espanyol fans retailed at Piqué and unfolded a banner with the words "Shakira es de todos" (Shakira is everyone's) written across it, angering the mayor, the news outlet further reported.

"To look at it damages your eyes," Colau told RAC1 on Thursday, as translated in ESPN FC's report. "I find it horrible. There are certain macho cultural values that can generate macho violence."

Espanyol's another banner read: "Pau, your foot shows us the way," commending club goalkeeper Pau Lopez for what looked to be an intentional stomp on the left leg of Messi during the first-leg tie, ESPN FC reported. The act angered Messi and caused him to confront Lopez before Suárez separated the two.

Espanyol is already facing potential sanctions after the Spanish courts council reported the team's racist chanting towards Brazilian star Neymar in the first of the latest matches between the sides on Jan. 2, SuperSport wrote. Possible sanctions may range from a fine to part or full closure of their Cornella-El Prat stadium located on the outskirts of Cornellà de Llobregat and El Prat de Llobregat.

"The banners and chants we saw last night at Cornella are unacceptable and will be studied by the anti-violence commission," president of the Spanish sports league, Miguel Cardenal, said on Thursday, as quoted in SuperSport's report.

Barcelona's president, Josep Maria Bartomeu, said that he hasn't seen the banners, but urged officials responsible for the match to ensure that measures will be taken to address the issue.

"I haven't seen [the banners] but they told me about them," Bartomeu told Sport. "It's what we talked about [before the game], the referee will have to take note and add it to his report."

According to the Guardian, Espanyol supporters also smuggled a pig's head at the Copa del Rey derby to throw at Piqué during Wednesday night's match. The pig's head, which was hidden in a paper bag, was revealed by fans to a local radio journalist.