The far-right and nationalists in Italy, Britain, France and Poland came out on top in their national votes on Sunday, shaking up politics at home but failing to dramatically alter the balance of pro-European power in the EU assembly.

At the EU level, provisional results published at on Monday showed the Socialists, Greens, liberals and conservatives with 506 of the 751 seats in the parliament that helps pass laws for more than 500 million Europeans.

While policy-making is likely to be difficult given the breakdown of a "grand coalition" of the centre right and centre left, the result shields the EU from anti-establishment forces seeking to break up the world's largest trading bloc.

"We are going to build a social Europe, a Europe that protects," Spain's Prime Minister Pedro Sanchez, whose revival among Spanish voters offset a fall in centre-left support in Germany, told a news conference.

President Emmanuel Macron's Renaissance platform, built on the ruins of French centre-left and centre-right parties, added to gains for liberals at the EU level while support for the Greens surged, giving four groups the pro-EU middle ground and holding on to two-thirds of seats.

Turnout in the world's second-biggest election rose to 51 per cent from 43 per cent in 2014, its highest in 20 years.

A stronger voice for the liberals and Greens could see the next EU executive seek a tougher line on regulating polluting industries, taxing multinational companies or demanding trading partners help contain climate change as well as press its own members, notably in the east, not to damage civil rights.

But disenchantment with the European project, which has struggled through economic and migration crises over the past five years, was palpable across the bloc.

Riding a wave of anger at the British government's failure to take the UK out of the EU, Nigel Farage's Brexit Party won a resounding victory, showing Britain even more polarised over its Brexit divorce.

In Italy, the far-right League became Italy's largest party, giving greater authority to its leader Matteo Salvini who is pushing for swingeing tax cuts in defiance of EU budget rules.

Poland's eurosceptic ruling Law and Justice party (PiS) also came out ahead. In France, Marine Le Pen's anti-immigration, anti-Brussels National Rally edged Macron's pro-European centrist movement.

In Germany, Chancellor Angela Merkel's conservatives lost votes from five years ago as the far-right Alternative for Germany gained. But the Greens grabbed the headlines, nearly doubling their vote to finish second, ahead of the governing Social Democrats.

Provisional results for the EU Parliament put the EPP on 179 seats, ahead of the S&D on 150, with the liberals on 107, up 39 seats, and Greens on 70, up 18. On the far-right, two groups in the parliament had well over a 100 seats, a 40 per cent jump from 2014.

The European Parliament election will usher in weeks and possibly months of hard bargaining over who will run EU institutions.

Australian Associated Press