Espanyol have been ordered to play their first two matches of next season behind closed doors after supporters chased Barcelona players down the tunnel at the Stage Front Stadium in May.
Hundreds of fans breached the security ring and entered the pitch following Barca's 4-2 win, which saw Xavi Hernandez's side clinch their first LaLiga title since 2019.
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Espanyol have said they will appeal the "disproportionate" punishment, which is due to affect their first two home games in the second division next season following relegation from LaLiga.
"As we have reiterated on multiple occasions, this type of behaviour has no place in football or society and we will continue to act in the most forceful way to eradicate it," a statement said.
"However, we feel that unreasonable criteria has been applied, inconsistent with other cases. It affects the entire club and season ticket holders from all sectors of the stadium.
"We consider the sanction disproportionate and, therefore, in defence of our legitimate interests and those of our fans, we will exhaust all means of appeal and protection at our disposal."
Tension was running high before the Catalan derby, with Barca aiming to win the league at their cross-city rivals and Espanyol needing the points to avoid relegation.
After claiming the three points which sealed the LaLiga title, the Barcelona players remained on the pitch for several minutes, celebrating in the centre circle.
Espanyol supporters then broke on to the pitch and charged at them, with the Barca players sprinting for the tunnel, which they reached without any major incidents.
Espanyol fans remained on the pitch, though, chanting anti-Barca songs before turning their attention to the directors' box and demanding president Chen Yansheng's resignation.
The mood against the club's Chinese owner has soured in recent years following two separate relegations from LaLiga.
They secured an immediate return to the top-flight after dropping into the second division in 2020 but, after two years back in the elite, they were relegated again last month following a draw against Valencia on the penultimate day of the season.