Eurosceptic nationalists made the biggest gains in European Parliament elections on Sunday while the Greens and liberals lost ground, an aggregated exit poll showed, a shift that may complicate EU policymaking and attempts to deepen integration over the next five years.

Far-right parties in France, Germany, the Netherlands, Austria, and elsewhere performed strongly in a vote that will see the balance of power shift rightward in the 720-seat parliament that helps shape and approve legislation across the bloc.

The impact of the EU vote was seen immediately in France, where President Emmanuel Macron unexpectedly called a snap parliamentary election after his party suffered a heavy defeat at the hands of the far-right National Rally.

The centralised exit poll showed the centre-right European People's Party (EPP) will be the biggest political family in the new legislature, gaining five seats to field 181 deputies.

The EPP result is good news for EPP member Ursula von der Leyen who seeks a second five-year term at the helm of the powerful EU executive arm. Von der Leyen will need the backing of both EU leaders and the parliament.

However von der Leyen may still need support from some right-wing nationalists, such as Italian Prime Minister Giorgia Meloni's Brothers of Italy to secure a parliamentary majority, giving Meloni and her European Conservative and Reformists (ECR) allies more leverage.

The centre-left Socialists and Democrats are poised to be the second biggest political family, even as they lost four lawmakers to end up with 135, the exit poll showed.

In contrast, the exit poll gave the ECR two more deputies than in the last parliament for a total of 71 and the far-right ID group 13 more seats for a total of 62.