UPDATE 6-Spain's Socialists seen ahead but short of majority in election

The Socialists of outgoing Prime Minister Pedro Sanchez were seen leading Spain's election as polls closed on Sunday, according to a survey by GAD3 published shortly after mainland voting ended.

The survey showed no single party close to winning a parliamentary majority. Far-right group Vox was seen winning lower house seats, making it the first party of its political hue to sit in Spain's parliament since 1982. Spaniards cast their votes in numbers close to record highs in the country's most highly-contested election for decades, and one likely to lead to months of negotiations to form a government in a bitterly divided parliament.

This is the third national election in four years, and both the first two eroded the decades-long dominance of the two biggest parties, the Socialists and the conservative Popular Party. Another repeat is a distinct possibility. A splintered vote followed by protracted talks to form an administration is becoming a recurrent theme in European politics as voters reject traditional parties in favour of new groups often at the extremes of the political spectrum.

In recent Spanish elections, early evening opinion polls carried out with a different methodology failed to give an accurate picture of the eventual outcome. (Additional reporting by Andres Gonzalez and Jesus Aguado; Writing by John Stonestreet and Sonya Dowsett)