Take a look at how people voted for their MEPs around Slovakia.
The Greens were set to win as many as three of the 13 European seats up for grabs and increase their local vote to 9% from less than 2% five years ago, according to a RED C exit poll for RTE/TG4, a showing that would put them in contention for government formation if repeated at a parliamentary poll.
Hundreds - if not thousands - of non-British EU citizens were turned away from polling stations on Thursday after being told they were not registered to vote in the United Kingdom for the election of the European Parliament.
Le Pen is seeking to strike a big blow to Emmanuel Macron's French presidency by overtaking his pro-European party Republic on the Move (LREM) and denying the young leader's ambition to shake up the EU.
Those parties hope to emulate what President Donald Trump did in the 2016 USA election and what Brexiteers achieved in the United Kingdom referendum to leave the European Union: to disrupt what they see as an out-of-touch elite and gain power by warning about migrants massing at Europe's borders ready to rob the continent of its jobs and culture.
Projections suggest the nationalist and far-right vote will be split between several smaller parties, which could prevent them from capturing seats in the European Union legislature.
Leading the challenge to the established order is Italy's hard-line interior minister, Matteo Salvini, head of the League party, who is assembling a group of like-minded parties from across Europe.More news: Post-election riots in Indonesia leave 6 dead, hundreds injured
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Turnout at the last European poll in 2014 was nearly 52 per cent, however, that coincided with a local government election.
Clara Kirchhoff said the election for the EU's 751-seat assembly was particularly important for tackling climate change on a continental level.
Britain and the Netherlands were first to vote, on Thursday, followed by Ireland and the Czech Republic on Friday and Slovakia, Malta and Latvia on Saturday, leaving the bulk of the 400 million eligible voters to join in on Sunday.
Fearing a wave of fake news the EU's External Action Service has set up a rapid alert system, with a dozen staff, to closely watch social media and warn of possible risks of interference.