The EU's traditional centre has splintered in the hardest-fought European Parliament elections in decades.
The far-right and pro-environment Greens gained ground on Sunday after four days of a polarised vote, with turnout at a two-decade high for ballots across all 28 European Union countries.
The elections were seen as a test of the influence of the nationalist, populist and hard-right movements that have swept the continent in recent years and seen Britain vote to quit the EU altogether.
Both supporters of closer European unity and those who consider the EU a meddlesome and bureaucratic presence portrayed the vote as crucial for the future of the bloc.
In Germany, Chancellor Angela Merkel's ruling coalition saw a drastic loss in support to the Greens and, to a lesser extent, the far right.
Italy's League party, led by Matteo Salvini, claimed 32 per cent of the vote in early projections, compared with around six per cent five years ago.
"Not only is the League the first party in Italy, but Marine Le Pen is first in France, Nigel Farage is first in Great Britain," Mr Salvini said.
"Therefore, Italy, France and England: the sign of a Europe that is changing, that is fed up."
Despite gains, the vote was hardly the watershed anticipated by Europe's far-right populists, who have vowed to dilute the European Union from within in favour of national sovereignty.
Pro-EU parties still were expected to win about two-thirds of the 751-seat legislature that sits in Brussels and Strasbourg, according to the projections released by the parliament and based on the results rolling in overnight.
The continent-wide voting had major implications not just for the functioning of the bloc but also for the internal politics in many countries.
Ms Le Pen claimed that the expected result "confirms the new nationalist-globalist division" in France and beyond; Greece's governing party called for snap elections after its loss; and Mr Salvini was expected to capitalise on the outcome to boost his power at home.
"The monopoly of power is broken," Margrethe Vestager, of the pro-EU ALDE grouping that includes Mr Macron's party.
Ms Vestager declared herself a candidate to lead the European commission for ALDE, which gained seats in large part because Mr Macron's party is itself a newcomer.
Ms Le Pen's far-right, anti-immigrant National Rally party came out on top in France with 24 per cent in an astonishing rebuke of Mr Macron, who has made EU integration the heart of his presidency.
His party drew just over 21 per cent, according to government results.
Exit polls in Germany, the EU's biggest country, likewise indicated Ms Merkel's party and its centre-left coalition partner also suffered losses, while the Greens were set for big gains and the far right was expected to pick up slightly more support.
Turnout across the bloc was put at 50.5 per cent, a 20-year high. An estimated 426 million people were eligible to vote.
The results will likely leave the EU parliament's two main parties, the European People's Party and the Socialists & Democrats, without a majority for the first time since 1979, opening the way for complicated talks to form a working coalition.
The Greens and the ALDE free-market liberals were jockeying to become decisive in the body.
Current MEPs' terms end on July 1, and the new parliament will be seated the following day.
Additional reporting the by the Associated Press