The exit poll by Catalonia's TV3 channel showed the "Together for Yes" group of secessionists winning 63-66 seats in the 135-member parliament. That's short of the 68 seats they needed for a majority to push forward their plan to make Catalonia independent from Spain by 2017.
But the radical left pro-independence Popular Unity Candidacy party was projected to win 11 to 13 seats in the parliament, which represents the northeastern region of 7.5 million people bordering France that is responsible for nearly a fifth of Spain's economic output.
The exit poll showed the pro-independence parties falling just short of that level, because of a quirk in Spanish election law that gives a higher proportion of legislative seats to rural areas with fewer voters. CUP leaders have also declared that they want an immediate declaration of independence rather than the 18-month secession roadmap favored by the "Yes" bloc.
Polls have closed in Catalonia and votes were being tallied. Final results were expected late Sunday or early Monday.
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The central government of Prime Minister Mariano Rajoy says it will use all legal means to prevent Catalonia from breaking away, an exit European leaders warn would include ejection from the European Union.
Spain's government has also said it is concerned that if Catalonia tries to break free it would disrupt the fragile signs of economic recovery for the country that has endured unemployment of over 22 percent for several years.
Many Catalans are also angry because they say their industrialized region, which represents nearly a fifth of Spain's economic output, pays too much in taxes and receives less than its fair share of government investment.