Polling stations across Catalonia saw long lines of people eager to cast their first vote since a referendum for independence from Spain triggered a months-long political crisis.
Thursday's early regional elections, announced by Prime Minister Mariano Rajoy's conservative government at the end of October, were one of several measures taken by Madrid after the Catalan parliament declared independence from Spain.
Voter surveys point to a neck-and-neck race between Catalan separatist parties and the so-called constitutional camps as Spain waits to see whether pro-independence parties can again win a majority of parliamentary seats and build a coalition government.
Turnout has so far been high. Some 34.7 per cent of all eligible citizens had cast their vote by 1 pm (1200 GMT).
Some 5.5 million Catalans are allowed to participate in the poll, with observers expecting an unusually high voter turnout of more than 80 per cent.
Sacked Catalonian ex-president Carles Puigdemont, currently campaigning for reelection while in exile in Brussels, sent a video message to his supporters on Twitter.
"Today is very important for the future of Catalonia. We hope to regain normality with this vote," said Puigdemont.
Madrid bumped up security in the region in anticipation of violence, with local media reporting that the Spanish Interior Ministry deployed some 15,000 police officers to patrol during voting hours.
Calm has so far reigned throughout the city. The same could not have been said 81 days ago when protesters clashed with police as they tried to shut down the independence referendum the Spanish central government said was illegal.
"Here's where they hit us," said Eli, a 35-year-old teacher at the Ramon Llull High School, which was the epicenter of the unrest.
"We had been here since 4 in the morning defending the school. But they took away the polls," she said.
The teacher was wearing a yellow ribbon - a symbol of solidarity with the pro-independence leaders, including electoral candidate Oriol Junqueras, currently incarcerated in Madrid for their role in the secession plan.
"It is not normal for candidates to be in prison and in exile on election day, to have intimidation of and intervention in our institutions," said Puigdemont in his video.
Catalonia, a wealthy region in Spain's north-east with a culture and language distinct from the rest of the country, was until recently led by the government of Carles Puigdemont, who held the independence referendum on October 1 and initiated a process of secession from Spain.
The move created a constitutional crisis, leading Rajoy's conservative government in Madrid to suspend the Barcelona government, place it under Madrid's control and call for new regional elections at the end of October. Catalonia's regular legislative period would have lasted until 2019.
Puigdemont and four of his ministers absconded to Brussels, while several other members of his administration were placed under arrest.
Polls are due to close at 8 pm (1900 GMT).
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