By Terje Solsvik and Jeremy Gaunt
COPENHAGEN (Reuters) - Denmarks's opposition "Red bloc" narrowly led a parliamentary election on Thursday, according to an early exit poll, threatening to oust the center-right "Blue bloc" after 10 years in power.
The survey by YouGov was released more than five hours before voting was due to end, and although turnout was already brisk, many voters were expected to go to the polls after work.
It indicated Denmark's Social Democrat-led opposition would win 89 out 175 seats in parliament, close to an overall majority.
The exit poll was not carried out in a further four seats, in Denmark's North Atlantic dependencies of Faroe Islands and Greenland, which take the total number of seats in parliament to 179.
Opinion polls had shown the Red bloc of Social Democrat Helle Thorning-Schmidt leading incumbent Prime Minister Lars Lokke Rasmussen's "Blue bloc," largely due to voter anger about Denmark's economic plight.
But the gap narrowed heading into Thursday's vote, which was taking place under more security than usual.
"It is going to be a tight race. We will fight to the end," Rasmussen said before heading off to cast his ballot.
A series of overnight polls showed the Red bloc leading with support of between 51.1 and 52.7 percent against 46.9 to 48.9 percent for the Blue bloc.
Rasmussen appealed to voters to stick with him.
"We (should) stay on the course that has (brought us) reasonably through the crisis, create new optimism in Denmark, not create obstacles to private consumption and not make it more expensive to be Danish," he said.
But Thorning-Schmidt, who would become Denmark's first female prime minister if she wins, argues that Rasmussen has failed to spur growth and taken the country deep into deficit.
"We can together create history this evening," she told reporters. "We can say farewell to 10 years of bourgeois rule that has stalled and get a new government and a new majority in Denmark."
Her platform includes increased government spending, along with a plan to make everyone work 12 minutes more per day. An extra hour of productivity each week, it is argued, would help kick-start economic growth.
IT'S THE ECONOMY
The state of the economy has been the overriding issue of the campaign, with the governing parties, like others in Europe, under fire for presiding over the worst downturn since World War Two.
Denmark has been spared much of the trauma suffered by west European countries because it remains outside the euro zone. This means it is not involved in bailing out debt-laden countries like Greece, an issue that has stirred popular anger in neighboring Germany.
But the economic crisis has turned Denmark's healthy surpluses into deficits, forecast to climb to 4.6 percent of GDP next year.
Danish banks have also been struggling, with small bank Fjordbank Mors falling into the hands of administrators in June, the ninth Danish bank to be taken over by the state since the start of the crisis in 2008.
Thorning-Schmidt, an ex-member of the European Parliament, is part of an extended European political family, married to the son of Neil and Glenys Kinnock. Neil was a European commissioner and British Labour Party leader, Glenys a European parliamentary deputy and Europe minister in the last Labour government.
Rasmussen, widely known by his middle name Lokke in part because he is Denmark's third unrelated Rasmussen prime minister in a row, is best known on the international scene for hosting failed U.N. climate change talks in Copenhagen in 2009.
(Additional reporting by Mette Fraende, Shida Chayesteh, Teis Jensen, Terje Solsvik, Ole Mikkelsen, Jakob Vesterager and Anna Ringstrom; Writing by Jeremy Gaunt; Editing by Mark Heinrich)