With turnout at a record high of 82 per cent, Thursday's election handed a mandate back to the region's ousted separatist leaders after they campaigned from exile and behind bars.
In a clear indicator of the huge gulf over independence afflicting Catalan society, anti-secessionist centrist party Ciudadanos won the biggest individual result with 37 of the 135 seats in the regional parliament.
But unless the three pro-independence lists fail to clinch a deal to work together in the coming months, they will rule Catalonia with 70 seats -- two less than their previous tally.
For Catalans on both sides of the divide the day had been a moment of truth, following weeks of upheaval and protests unseen since democracy was reinstated following the death in 1975 of dictator Francisco Franco.
Emboldened, separatists saw the vote result as vindicating their cause.
"This is a result which no one can dispute," deposed leader Carles Puigdemont said from self-imposed exile in Belgium.
"The Spanish state was defeated. (Spanish Prime Minister Mariano) Rajoy and his allies lost," he told reporters.
Defeat for Rajoy
The Spanish government called the election after it took the unprecedented step of stripping Catalonia of its treasured autonomy in the aftermath of an independence declaration on October 27 that rattled a Europe already shaken by Brexit.
At stake was the economy of a region that has seen its tourism sector suffer and more than 3,100 companies -- including the largest banks, utilities and insurers -- move their legal headquarters out of Catalonia.
The declaration came weeks after a banned independence referendum on October 1, which was marred by a brutal police crackdown.
Rajoy and his conservative cabinet tried to nip the independence movement in the bud, sacking the regional government and dissolving its parliament.
In a further obstacle for the separatist cause, the judiciary pressed charges of rebellion, sedition and misuse of funds against the secessionist leaders.
Puigdemont, who had fled to Belgium where he tried to rally international support for the separatist cause, has not since returned to Spain, where he faces arrest.
So far the EU has backed Rajoy, saying it supports constitutional order, and that it is an internal matter for Spain.
The European Commission stressed its stance remained the same regardless of the result of the vote.
Puigdemont's Together for Catalonia list secured the best result of the three separatist groupings -- in a major upset for Rajoy.
"2018 will likely be the year in which it will become clearer whether or not Rajoy can survive for a full term," he added.
'A bitter victory'
What the separatists' victory will mean in practice, however, remains a mystery.
"It is unclear whether Puigdemont will be able to be re-appointed... as he will be arrested if he comes back to Spain," Barroso said.
"As a result, the investiture process will be far from straightforward, and the risk of new elections in 2018 remains high," he added.
Puigdemont is to hold a press conference in Brussels at 1030 GMT Friday.
Rajoy, who has not commented so far, may speak in the afternoon after a meeting of his party, which saw its number of seats in the Catalan parliament slashed from 11 to just three.
In Belgium, a separatist supporter warned against triumphalism.
"It's a bitter victory," said Michel Vila, a 70-year-old retired engineer who has lived in Belgium for 30 years.
Crucially, the pro-independence camp is not expected to attempt another breakaway from Spain but rather try to enter into negotiations with Madrid -- even though Thursday's result certainly strengthens the separatists' hand.
The Catalan business elite, some of whose members have close links with Puigdemont's party, "know that they have to give a fresh boost to tourism and the economy", sociologist Narciso Michavila told AFP.
On the other side of the divide, Ciudadanos candidate Ines Arrimadas saw the glass half full, celebrating her centrist party's lead in votes.
"The nationalists will never again be able to speak in the name of all Catalonia. We are all Catalonia," she said in a speech to supporters after the result.
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