Rome - Rival populist leaders were left fighting for the right to govern Italy after their surge in a general election left the country in political limbo.

The anti-immigrant League party and the anti-establishment Five Star Movement (M5S) each claimed Sunday's vote gave them a mandate to lead the nation of 60 million.

League leader Matteo Salvini said on Monday that he had "the right and the duty" to form a government after its surprise success at the heart of a right-wing coalition.

But M5S, which won the biggest share of the vote of any single party, claimed it was the winner. Its leader Luigi Di Maio said it had a "responsibility" to form a government.

The boost for far-right and populist parties has prompted comparisons to Britain's vote to leave the European Union and the rise of US President Donald Trump.

Former White House adviser Steve Bannon -- the man who helped Trump ride a populist wave to power -- described the results as "an earthquake" in an interview with Swiss weekly Die Weltwoche.

"The tremor is going to continue... there's really a populist national revolt (against the EU), it's building steam," Bannon, who was in Rome for the election, said.

- Anti-immigrant promises -

With most ballots counted, the League was leading the dominant right-wing coalition, which won roughly 37 percent of the vote overall.

The League by itself was closing in on 18 percent, ahead of former prime minister Silvio Berlusconi's Forza Italia (Go Italy) party, which collapsed to 14 percent.

Salvini's party surged in the polls after promising to shut down Roma camps, deport hundreds of thousands of migrants and tackle what it calls the "danger" of Islam.

Maps of Italy showing the results of the parliamentary elections as of 1425 GMT

However much depends on M5S, which has drawn support from Italians fed up with traditional parties and a lack of economic opportunity.

It won 32 percent of the vote.

The M5S had previously refused to align itself with other parties, which it considered part of a "corrupt" system.

But Di Maio said his party now "feels the responsibility to form a government".

To that end, he said he was "open to discussion with all political actors".

"This election was a triumph for the Five Star Movement. We are the winners," a joyous Di Maio told a news conference on Monday.

- Five Star League? -

According to polling company YouTrend, the M5S was set to gain 231 seats in the lower house Chamber of Deputies and 115 in the upper house Senate.

It could therefore form a majority with either one of the League, Forza Italia and the Democratic Party (PD).

Given its heated rivalry with the PD and Berlusconi, M5S's most likely ally looked to be the eurosceptic League.

However Salvini swiftly ruled out the prospect of forming a coalition with the M5S.

"N. O. No, underlined three times," Salvini told reporters.

Negotiations could take weeks, or even months.

"We won't have a government any time soon," Antonio Risconi, a resident of Milan, said as ballot counting continued.

Andrea Leo, also from Milan, said that if Italians had voted for traditional parties "nothing would have changed for sure.

"At least now there is a possibility for change," he said.

- 'Bad night' for EU -

Prominent British pro-Brexit figure Nigel Farage congratulated M5S, his allies in the European Parliament, "for topping the poll" as by far Italy's biggest single party.

Marine Le Pen, leader of France's National Front, tweeted that it was a "bad night" for the EU.

Resentment at the hundreds of thousands of migrant arrivals in Italy in recent years fired up the campaign, along with frustration about social inequalities.

"These are historic results," Giancarlo Giorgetti, deputy head of the League, told reporters in Milan.

Alessandro Di Battista, another senior Five Star leader, said: "Everyone is going to have to come and speak to us".

PD leader Matteo Renzi looks doomed after his party dropped to 19 percent of the vote.

- Germany hopes for 'stable government' -

Berlusconi, a flamboyant three-time former prime minister, is on the ropes after his electoral flop.

The billionaire, who won his first election in 1994, has returned to the limelight at the age of 81 despite a career overshadowed by sex scandals and legal woes.

But he has turned out to be the big loser alongside Renzi.

The election campaign was marred by clashes between far-right and anti-fascist activists, as well as a racist shooting spree by an extreme-right sympathiser last month.

German Chancellor Angela Merkel's spokesman Monday wished post-election Italy success in forming a "stable government", adding that he hoped Rome would not take six months as Berlin just did.

"Italy is our friend and partner, and we wish those responsible success in forming a stable government, for the benefit of Italians as well as of our common Europe," said Steffen Seibert.

By Lucy Adler