Riot police forcibly removed people in scuffles and kicked in the door of a school in Barcelona on Sunday.
The confrontations occurred as voting started in a banned referendum on the region's secession that has challenged Spain's political and institutional order.
In Girona, Spain, clashes erupted between the Spanish Civil Guard and voters outside a polling station.
Catalan leader Carles Puigdemont was expected to vote at that station, but cast his vote in a nearby village.
Spain's Constitutional Court ordered the vote to be suspended and central authorities say the vote is illegal.
More than 300 people have been hurt in the clashes.
Regional separatist leaders have pledged to hold it anyway, promising to declare independence if the 'yes' side wins, and have called on 5.3 million eligible voters to cast ballots.