The most likely result of the national election seemed either a win by the centre-right coalition headed by Silvio Berlusconi, the 81-year-old former prime minister, or a hung parliament in which populist parties - the anti-establishment Five Star Movement and the xenophobic Northern League - would have considerable influence in the creation of a new government.
If the centre-right fails to clinch a majority, then the Five Star Movement, an anti-establishment party that was founded nine years ago by former comedian Beppe Grillo, will emerge as the single most powerful party in Italy and decisive in a future coalition, having won up to 31% of the vote, according to early results that were not yet final.
The centre-right, which includes Mr Berlusconi's Forza Italia (Go Italy!), and the far-right League and Brothers of Italy, were seen falling some way short of an absolute majority, pollsters said.
During the Sunday election, polls opened from 7am until 11pm across the Italy.
People wait in line to cast their ballot at the polling station in Rome on Sunday, March 4, 2018.
None of the populist forces are expected to receive enough votes to govern alone. Paolo Gentiloni of the Democratic Party has been a caretaker prime minister since Matteo Renzi resigned after his referendum to reform the Senate failed in December 2016.
"Di Maio could change strategy and give up some ministers' jobs but that would be risky for him because many of his voters don't want deals with other parties", said Fabio Bordignon, a political science professor at the University of Urbino who has studied the party's rise.
GETTYMatteo Salvini is the leader of Lega Nord
The Democratic Party, which now heads the government under leader Matteo Renzi, was the next largest party. But he says he could play a key role from the sidelines and has flagged European Parliament head Antonio Tajani as his candidate for the premiership. Their hard-to-categorise policies are determined by an unusual system of direct online voting among their party members, and they have not taken clear stances on some of main issues facing Italy in the world, such as European Union integration and the future of economic sanctions against Russian Federation.
A new law passed past year, ostensibly to make Italy more governable, calls for a combination of direct and proportional voting for members of Parliament.
Of the 630 seats in lower house of Parliament - the Chamber of Deputies - 232 will be elected through FPTP, and 386 through PR.
The new law calls for roughly a third of the seats to be selected by the direct "first-past-the-post" system, with the remainder selected by proportional outcomes divided among allied parties and coalitions.
Five-Star would get between 195 and 235 seats.
Election turnout was 71.48%, the Interior Ministry said, a slight drop from the 75% of eligible voters who participated in the 2013 election. This would give the center-right coalition brokered by Berlusconi the most votes, including votes for the smaller Brothers of Italy Party, which is also in the coalition. The next prime minister will have to win votes of confidence in both houses of parliament.