Earlier on Wednesday, the demonstrators engaged in clashes with police, throwing cans, bottles and stones on security officers. The police, in their turn, used batons to push back the demonstrators.
Later, Spanish police reported Catalan pro-independence demonstrators threw petrol bombs at officers.
"Molotov cocktails launched at the police line," the Mossos regional police force posted on Twitter.
23.08h Llançament de còctels molotov a la línia policial a Gran Via amb el carrer Nàpols. No us apropeu a la zona i seguiu indicacions policials pic.twitter.com/S24CrXKWS4— Mossos (@mossos) October 16, 2019
The footage published by the 24 Horas news outlet late on Wednesday showed the radical protesters overturning the trash bins, setting them on fire and setting up the barricades. Moreover, the footage showed several cars burning.
El pobre noi estès a terra, sense moure's pic.twitter.com/ubd7wSL06u— Mimi Sen Gav (@SenGav) October 16, 2019
The unrest also erupted in the city of Girona, where the demonstrators were throwing various things security officers outside the Spanish government representative office, El Pais reported.
According to the urban guard — the Barcelona city police — 22,000 people participated in a protest, organized by the pro-independence Committees for the Defence of the Republic, which turned violent.
The protesters in both Barcelona and Girona called for the resignation of Miquel Buch, the adviser on domestic affairs to the government of Catalonia, who condemned the actions of radical independence activists earlier on Wednesday.
Late on Wednesday, a fresh wave of protests began across Catalonia.
In Barcelona, which saw the largest number of rallying activists, the protesters gathered at Gran Via de les Corts Catalanes avenue. The footage published by 24 Horas showed the demonstration throwing toilet paper rolls in the air as a symbol of a need to "clear up a lot" in the region.
A demonstration is also underway in the city of Lleida.
In Madrid, supporters of the jailed Catalan pro-independence politicians gathered at the Puerta del Sol square, chanting "Freedom!"
The demonstrations have been rocking Catalonia since Monday when the Spanish top court ruled to give prison terms of up to 13 years to nine politicians for their role in the 2017 unauthorized regional independence referendum. Moreover, an international arrest warrant has been issued for ex-Catalan government head Carles Puigdemont, who then led the independence movement and has fled to Belgium after the crisis erupted.
Though the jailed politicians called for the protests to be peaceful, the violence continued.