More than 800 people are reported to have been injured in the clashes, which saw riot police smashing their way into polling stations and beating voters.
Catalan officials said the preliminary result of the referendum showed 90% of voters backed the formation of an independent republic.
After the vote, Catalan leader Carles Puigdemont told the BBC on Wednesday the autonomous region would declare independence from Spain “at the end of this week or the beginning of next”.
The Spanish government responded by accusing Catalonian separatists of “blackmail”.
The European Commission sided with Spain in a statement, which deemed the independence vote “not legal” under the Spanish constitution and called for all parties involved to seek “unity and stability”.
“If a referendum were to be organised in line with the Spanish Constitution it would mean that the territory leaving would find itself outside of the European Union,” the statement read.
Catalonia independence referendum: Riot police clash with voters
Show all 17
Catalan businesses are considering moving out of the region due to the threat of an impending independence declaration and the region’s political stability, with Barcalona-based Sabadell bank already announcing plans to move its head office to the city of Alicante.
Spain’s third-largest lender Caixabank has said its board will meet on Friday to consider transferring its legal base out of Catalonia to the Balearic Islands.
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies
Join our commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies