Supporters of the Spanish Socialist Party (PSOE) celebrate victory at its headquarters in Madrid, Spain, on April 28, 2019. The Spanish Socialist Party of Prime Minister Pedro Sanchez led in the Spanish election on Sunday when 95.6 percent of the votes were counted, but will need to pact with other parties to form a government. (Xinhua/Guo Qiuda)

Prime Minster Pedro Sanchez said his Spanish Socialist Party (PSOE) has "won the future and left the past behind" after the party took lead in Sunday's general election.

According to data published by the Spanish Interior Ministry with over 99 percent of the votes counted, the PSOE won 28.70 percent of the votes to win 123 seats in the 350 seat Spanish Congress of Deputies.

This means the PSOE had 37 more seats than in the June 2016 election when the Socialists won 22.63 percent of the vote and 85 seats.

Sunday saw the Socialists win 57 more seats than the right wing People's Party (PP), who ranked second in the election, but saw their vote share plunge from 33.01 percent in June 2016 to 16.69 percent on Sunday as support for right wing parties was split into three.

The PP lost votes to Albert Rivera's center-right party Ciudadanos, which gained 15.85 percent of the votes and won 57 seats, while the extreme right wing Vox claimed 10.26 percent of the votes to enter Congress for the first time with 24 seats.

Sanchez said that "the victory of the left against the right-wing block" showed that Spaniards "don't want to go backwards, but want a country that looks to the future."

"We have also sent a message to the Spanish people, Europe and the world that you can win against reactionaries and authoritarianism," he added.

Although he will now need to form a coalition government, Sanchez was clear the election was "a question of winning and governing," and that "we have won the election and we are going to govern Spain."

Sanchez said he would form a "pro-European" government.

Thousands of Socialist supporters chanted "with Rivera no!" in the street outside the PSOE headquarters on two occasions, making it clear they do not want to see a coalition with Ciudadanos.

Although Sanchez said he had "heard" the chants, he insisted he and his party would be "the prime minister and the government of all Spaniards," and would extend their hands to "all constitutionalist parties."

"I am not going to put a safety cordon around us," he added.

Finally, Sanchez said that his government's ambitions would be to "advance" and work to "end inequality," while attempting to lower the "political tension of recent years" and the "corruption" that has dogged the country.

Although Sanchez failed to rule out a pact with Ciudadanos, it still looks as if the PSOE will look to form a coalition government with the left wing Unidos-Podemos party.

Unidos-Podemos saw their vote share fall from 16.97 percent to 14.31 percent and the number of representatives reduced from 71 to 42.

Podemos leader Pablo Iglesias said that although he was "disappointed" with the result, it had "fulfilled out two aims, which were to stop the right and the far right and to form a coalition government with the left," although he predicted talks could be long and complicated.