Spanish voter turnout recovered in the afternoon, taking total voter numbers above 2011 levels.
Of those eligible to vote, 58.3 per cent had hit the voting booth by 6pm, Spain's interior ministry said today. It marks a rise from 58.6 per cent in 2011.
Turnout had risen strongly in the north and east of Spain compared with the 1pm figures.
Around 220,000 fewer people had voted by 1pm on Sunday compared with the November 2011 general election, with turnout falling to 36.9 per cent, down from 37.9 per cent, the government said.
There will be a second turnout estimate at 5.30pm before voting closes at 7pm.
The government will announce provisional results at 9.30pm.
Too early to make too much of #SpainElection low turnout reports but also not entirely surprising given polls showed huge num of undecided— Raoul Ruparel (@RaoulRuparel) December 20, 2015
Why are these elections important?
The two party system that has dominated Spanish politics in recent decades is set to come to an end, with newcomers Cidudadanos, a centrist party, and left-wing Podemos rapidly gaining ground on the traditional parties.
“All bets are off. Spain is heading towards the most indecisive general election since the return of democracy in the late 1970s, with the most recent polls pointing to a hung parliament,” said economist Yvan Mamalet from Societe Generale.
"With close to 20 per cent of voters undecided and an electoral system that tends to favour rural areas and the largest parties in each constituency, the probability of a surprise on election night appears non-negligible."
Prime Minister Mariano Rajoy’s centre-right People’s Party (PP) will get the most votes, according to polls in the run up to the election, but will not secure a majority in Spain’s 350-seat parliament. It means Rajoy could be leading a minority government or a coalition.
The most recent polls are implying a coalition between of PP and the centre party Ciudadanos is a likely scenario.
The other main party, the Spanish Socialist Workers' Party, could also pip PP to the post. Should it opt to form a coalition with Podemos, the government may undo many of Rajoy's labour market reforms spending cuts.
Should Podemos earn a place in a coalition government, it is not expected to have as big an impact as its sister party Syriza had in Greece.
Holger Schmieding, chief economist at Berenberg Bank, played down the threat to the Eurozone from a Podemos victory. He said:
Reform reversals would be bad for Spain. But thanks to the adjustment progress of the last five years, the blow would not be fatal. Having watched the sorry fate of Greece in 2015, even Podemos has become less radical. The risk that any new Spanish government could adopt policies that would jeopardise Spain’s place in the euro or even trigger some kind of new euro crisis looks small.