Voters in 21 EU countries including France and Germany will conclude a four-day election for the European Parliament on Sunday, which is expected to shift the assembly to the right and boost the numbers of eurosceptic nationalists.

The election will shape how the European Union, a bloc of 450 million citizens, confronts challenges including a hostile Russia, increased industrial rivalry, climate change and immigration.

The election began on Thursday in the Netherlands and in other countries on Friday and Saturday, but the bulk of EU votes will be cast on Sunday, with France, Germany, Poland and Spain opening the polls and Italy holding a second day of voting.

Opinion polls predict the pro-European liberals and Greens will lose seats, reducing the majority of the centre-right and centre-left and complicating efforts to push through new EU laws or increase European integration.

Many voters have been hit by the cost of living crisis, have concerns about migration and the cost of the green transition and are disturbed by rising geopolitical tensions, including the war in Ukraine.

Hard and far-right parties have seized on this disquiet and offered the electorate an alternative to the mainstream.

European Greens, facing a backlash from hard-pressed households, farmers and industry over costly EU policies limiting CO2 emissions, look set to be among the big losers.

Forecasts for the liberal group Renew Europe are also grim, given the expectation that Marine Le Pen's far-right Rassemblement National will trounce French President Emmanuel Macron's centrist Renaissance in France.

In the Netherlands, exit polls from Thursday already showed nationalist Geert Wilders' anti-immigration party was set to win seven of the 29 Dutch seats in the EU assembly, from zero in 2019, following up on his large win in last year's national election.

In Belgium, voters will also get to elect federal and regional chambers and are forecast to back the far-right Flemish separatist party Vlaams Belang in record numbers, although it could still be kept from office by other parties. (Reuters)