By Julien Toyer
BARCELONA (Reuters) - Separatist parties are expected to win control of Catalonia's parliament in an election on Sunday, setting the region on course for a unilateral declaration of independence which Spain's central government vows to block.
A high turnout could lead to a last-minute surprise, but opinion polls showed the main secessionist group "Junts Pel Si" (Together for Yes) and leftist party CUP likely to win a majority of seats in the 135-strong assembly, despite falling short of 50 percent of the vote.
Both have said that such a result would allow them to unilaterally declare independence within 18 months, under a plan that would see the new Catalan authorities approving their own constitution and building institutions like an army, central bank and judicial system.
The Spanish centre-right government of Prime Minister Mariano Rajoy, which has opposed attempts to hold a referendum on secession, has called the breakaway plan "a nonsense" and vowed to block it in court. Spain's constitution does not allow any region to break away.
Markets will also be watching the vote outcome. Spain's banks, including some based in Barcelona, have warned secession could cause financial turmoil, while the Bank of Spain has said Catalonia could risk exiting the euro.
Regional government head Artur Mas has said the only way forward for Catalonia is a split from Spain, but many of the 5.5 million voters said on Sunday they did not believe it would become independent.
Some said they had used their ballot as a way to press the Catalan and Spanish authorities to discuss a more favourable tax regime as well as laws that better protect language and culture.
Carmen Marfa, a 65-year-old pensioner from Barcelona who voted for Junts pel Si said she wanted negotiations on those issues to start right after the election.
"Politicians have to roll up their sleeves now, stop their game of chicken and make concessions," she said after casting her ballot.
Jose Luis Bonet, a 43-year-old architect, said the election was highly confusing and gave a bad image of Spain and Catalonia to the world.
Bonet, who voted for the socialist party, said he was not in favour of independence but that the Spanish state should have accepted holding a referendum on the issue.
"This election is shameful. It would have been much better to organise a vote like in Scotland with debates and proper information so that voters can make up their mind," he said.
HIGH TURNOUT
The turnout at 1600 GMT was 63 percent, 7 percentage points higher than at the same stage of the last regional elections in 2012, and on track to be the highest on record since the end of the Franco dictatorship in the 1970s.
"In principle, such a high turnout could indicate that those who usually vote in countrywide elections but don't routinely do it in regional elections mobilised this time around, and their vote is basically in favour of the constitution," said Jose Pablo Ferrandiz from polling firm Metroscopia.
Any failure to achieve a majority of seats would deal a serious blow to the secessionist campaign, which is facing a defining moment after steadily losing support since a peak in 2013.
The vote is also set to influence the course of the Spanish general election in December.
The main national parties, all seeking to capture more votes in Spain's second most populous region, have said they are ready to discuss with Catalonia a more favourable tax regime and increased infrastructure spending if they win.
Depending on who forms a government in Madrid, constitutional reform to recognise Catalonia as a nation within the Spanish state may even be on the cards.
"Only when a final package (of reforms) is adopted and put to a vote will the problem find some form of resolution," Teneo Intelligence analyst Antonio Barroso said in a note this week.
"Even if secessionist parties are able to remain united - a big if - and continue pushing for independence, any concessions from Madrid would probably help to stymie the movement's momentum," he also said.
While few investors believe independence is likely soon, the gap between Spanish five-year bond yields and the higher yields of the Catalan equivalents has been hovering near its widest point in two years.
(Additional reporting by Elena Gyldenkerne; Editing by Andrew Roche)
