Spain's far-right Vox party won 12 seats in an election in Andalusia on Sunday and could end up as a kingmaker in the country's most populous region, according to preliminary results with almost 98 percent of the vote counted.
The preliminary official results showed the Socialists, who have ruled the southern region since Spain's return to democracy, getting most votes, but falling well short of a majority with only 33 of the regional parliament's 109 seats.
Votes were widely distributed and it was arithmetically possible that the conservative People's Party and Ciudadanos could form a majority coalition with Vox's backing.
This would rattle national politics, with a series of local, regional and European elections scheduled for May.
The preliminary results showed the People's Party obtained 26 seats and the center-right Ciudadanos 21.
The vote was the first electoral test for both Socialist Prime Minister Pedro Sanchez and the new leader of the conservative People's Party, Pablo Casado.
With the far-left Podemos getting only 17 seats, the Socialists would have to seek other allies if they want to keep power in Andalusia.
French far-right leader Marine Le Pen tweeted: "Strong and warm congratulations to my friends from @Vox, who tonight in Spain scored a very meaningful result for such a young and dynamic movement."
The election took place in a political landscape in which major parties find it harder and harder to secure majorities. Vox was founded at the end of 2013.
The next national election is due in 2020 but speculation has been rife for months that Sanchez, who controls fewer than a quarter of seats in the Madrid parliament, could call a snap vote.
Senior Socialists said before the election in Andalusia that they did not expect it to trigger a general election.
Andalusia has one of the highest unemployment rates in Europe and is the main arrival point in Spain for migrants crossing the Mediterranean. The number reaching Spain has grown in the past year as traffic on the main sea route to Europe, from Libya to Italy, has slowed.