Italy's anti-establishment Five Star movement fired a warning shot across Prime Minister Matteo Renzi's bows Monday with a landmark victory in the first round of Rome's mayoral race.

Five Star (M5S) candidate Virginia Raggi looked likely to become the capital's first female mayor after winning the first round with more than 35 percent of the vote, according to final results.

Raggi's success came amid anger over corruption scandals in the Eternal City and mirrored the rise of populist and anti-establishment parties across Europe.

Roberto Giachetti of Renzi's centre-left Democratic Party (PD) came a distant second with less than 25 percent.

Coming a close third was Giorgia Meloni, a candidate fronted by one of several small groups that emerged from Italy's neo-fascist movement, who took 20.6 percent.

"We are ready to rule, let's change everything," wrote M5S founder and comedian Beppe Grillo on his blog.

The victory will now see the 37-year-old Raggi, a lawyer with a tough line on corruption, going up against her 55-year-old rival in a June 19 run-off, with experts predicting she will triumph.

Losing control of Rome would not bode well for Renzi four months before a referendum on constitutional reforms designed to end decades of gridlock in parliament.

The 41-year-old premier has vowed to resign if voters reject the reforms.

- 'PM should be worried' -

"Unless there is a startling and dramatic turn in events, the capital is going to have a 'Grillino' mayor," political commentator Stefano Folli said in the La Repubblica daily, using a nickname for the movement's members.

"The optimism and hope in the future needed if voters are to back the ruling party proved too weak. This should worry the prime minister, considering the challenges of the coming months," he said.

The Italian capital has been without an elected leader since last October, when PD member Ignazio Marino was forced to quit over an expenses scandal.

The city is also still dealing with the fallout from Mafia Capitale, a scandal that erupted in 2014 when dozens of businessmen, politicians and officials were arrested on suspicion of conspiring for years to siphon off city funds through rigged tenders and other scams.

During the second round, Giachetti could potentially pick up around 11 percent of support from a centre-right coalition ally although no such agreement has yet been inked.

But that would pale in comparison to the more than 20 percent worth of support Raggi was likely to get from Meloni, who is backed by the anti-immigrant Northern League whose leader Matteo Salvini wants to unite all the right behind himself.

"I would never, ever vote for a PD candidate... even under torture. So in the event of a tie... I would vote for Raggi," Salvini said last month.

- 'Historic moment' -

A Five Star win in Rome would boost the populist movement -- founded in 2009 by Grillo, a wild-eyed and outspoken comedian -- as it seeks to cement its status as a mainstream party.

"Romans are sending a clear message. We are witnessing a historic moment," Raggi said in her victory address.

The "Grillini" will be hoping the victory will give them the platform they need to transform themselves into Italy's principal opposition in the run-up to national elections due by June 2018 at the latest.

But experts have warned it could be the movement's undoing, landing a politically inexperienced team with a city not only plagued with corruption, refuse and transport problems but notoriously difficult to manage.

"Winning in Rome would land them with a hot potato. I hope for their sake they do not," Piergiorgio Corbetta, research director at the Cattaneo di Bologna institute, told AFP.

Overall, more than 13 million people nationwide were asked to cast their ballots to choose members of 1,300 municipal councils in a two-round ballot.

Renzi, who played little part in most of the elections, played down their significance ahead of the vote, saying they were "about mayors, the people whose job it is to repair the streets, not the government of the country".

But on Monday he told reporters that while Giachetti had "performed a minor miracle" by coming second in Rome after the problems with the outgoing mayor, "we are not happy".

And in Naples, where Renzi had personally rolled up his sleeves for a PD victory, the ruling party failed to make it even to the second round.

Source: AFP