Spain's Socialist party has pledged to act fast to form a government after its leader and acting prime minister Pedro Sanchez gambled on a repeat election that resulted in no clear winner but a surge for the far right.
A polarised electorate awarded neither right nor left-wing parties enough seats to govern with a majority in Sunday's vote - Spain's second this year and its fourth since 2015 - although the Socialists won most seats.
"We will try to keep our promise to form a government as quickly as possible because the country needs it," senior Socialist official Jose Luis Abalos told broadcaster Radio Nacional.
Asked whether a new vote might be called, Abalos said: "I totally rule it out. It would be an institutional failure."
Sanchez's Socialist Workers' Party of Spain (PSOE) won 120 of the 350 parliamentary seats - three fewer than in April.
The conservative People's Party (PP), which alternated in government with the Socialists for decades after Spain emerged from General Francisco Franco's dictatorship in the 1970s, recovered from a disappointing result in April to take 88 seats.
But the centre-right Ciudadanos slumped from 57 seats to just 10 and was replaced as the third-largest parliamentary group by the far-right Vox, a relative newcomer, which secured 52 seats.
Sanchez has ruled out forming a broad coalition with the People's Party, and he failed to strike a deal earlier this year with far-left Unidas Podemos, but he will need at least tacit support from other parties to be named prime minister.
In Spain, opposing parties can smooth the way for their rivals to form a government by abstaining in the second round of a parliamentary confirmation vote.
Senior PP official Teodoro Garcia Egea told Onda Cero radio on Monday that Sanchez had not asked his party to do so.
"Sanchez has not asked us to abstain, but even if he did we wouldn't give it to him because we don't trust him," he said.
Unidas Podemos lost seven seats to take fourth place with 35 seats.
Its leader Pablo Iglesias said he was ready to start negotiating with Sanchez and urged the left to unite this time.
Joining a nationalist wave in other parts of Europe, Vox's anti-immigrant stance and particularly vehement opposition to a secessionist drive in Catalonia has become the first far-right party to win more than one parliamentary seat since Spain returned to democracy.
With many Spaniards still remembering the Franco years, the country had long appeared immune to right-wing nationalism. But Vox leader Santiago Abascal said he would now work to build what he called "a patriotic alternative" for Spain.
Australian Associated Press
