Spanish Prime Minister Pedro Sanchez looks set to regain power after his Socialists overcame a historic election challenge by right-wing nationalists, a result he portrayed as a European Union morale booster.
The Socialists gained seats in one of Spain's most hotly-contested elections in decades, which featured the rise of far-right party Vox, whose nationalist campaign echoed political trends across Europe.
However, the rise of Vox splintered the right-wing vote, further fragmenting Spain's political landscape and playing into the hands of the Socialists, which won an almost 50 per cent increase in seats.
"Social democracy has a great future because it has a great present and Spain is an example of that. We will form a pro-European government to strengthen and not weaken Europe," Sanchez told supporters.
Outside party headquarters in Madrid, hundreds celebrated, waving red party flags and chanting "Long live Spain" and "Long live Socialism".
The result is likely to come as a relief for supporters of further EU integration ahead of May 26 elections for European Parliament.
Vox secured one in 10 votes and 24 seats, the first far-right party to get a sizeable presence in parliament since the country's return to democracy in the 1970s, but it did not get the kingmaker role it sought.
Far left-wing Podemos immediately offered to open coalition talks with Sanchez, though the two parties together cannot command a majority. Bridging the gap would require Sanchez to rely on Basque nationalists and small parties.
It was unclear in the early hours of Monday if he would also require the support of separatist lawmakers from Catalonia, the country's richest region, where an independence push flared into violence two years ago.
According to Sunday night's count, Sanchez would require one Catalan separatist lawmaker to abstain but some seats were too close to call. The picture may still change when the count is finalised in early May.
If Sanchez does not need to rely on Catalan separatists, who brought down his minority government, he may have more political freedom to deal with the Catalan independence movement. The issue was at the heart of the election campaign, at times unnerving Eurozone investors and the EU.
Alternatively, Sanchez could turn to centre-right Ciudadanos. Together, the Socialists and Ciudadanos would have an outright majority.
Though he and Ciudadanos leader Albert Rivera have sharply different views on Catalonia and both ruled out forming an alliance during the campaign, speculation persists the pair could yet strike a coalition deal. Rivera repeated after the election that he would be in the opposition.
Spaniards cast their votes in numbers close to record highs with campaigning dominated by national identity and cultural values like women's rights.
This is the third national election in four years, after the first two eroded the decades-long dominance of the two biggest parties, the Socialists and the conservative Popular Party (PP).
By party, Sanchez's Socialists led with 123 seats in the 350-seat parliament. The PP stood at 66, centre-right Ciudadanos at 57, Podemos at 42 and Vox at 24.
The big loser was the PP, which lost more than half its seats in the lower house of parliament and also lost control of the senate to the Socialists.
