Pro-European Dutch parties were predicted Thursday to win most of the country's seats in the European Parliament, with right-wing populist opponents of the European Union managing to take only four of the nation's 26 seats.

In a surprise forecast, the Dutch Labor Party of European Commission Vice President Frans Timmermans became the country's biggest party in the 751-seat European Parliament, according to an Ipsos exit poll.

"What an unbelievable exit poll!" Labor leader Lodewijk Asscher told a gathering of cheering party faithful.

The poll was published by Dutch national broadcaster NOS after polling stations closed Thursday evening in Netherlands. Earlier in the day, Dutch and British voters kicked off the first of four days of voting for the European Parliament in all of the EU's 28 nations.

Official results will only be announced after the last polling station in the EU closes late Sunday.

The Dutch Labor Party was forecast to win five seats, while the pro-European center right VVD of Dutch Prime Minister Mark Rutte gained one seat to win a total of four seats.

"There is a clear majority of people in the Netherlands, if you count them altogether, who want the European Union to continue playing a role in tackling problems that need to be solved," Timmermans told NOS, speaking from Spain.

"I realize that everywhere in Europe there is a need for another Europe, one that fights harder against climate change, that we have to cooperate on a social level, and where big business has to pay more taxes."

Timmermans is a broadly respected former Dutch foreign minister who is trying to become the next president of the European Commission.

The Dutch right-wing populist group Forum for Democracy of climate-sceptic populist leader Thierry Baudet was forecast by the Ipsos exit poll to win three seats in its first European elections, but those gains didn't primarily come at the expense of Europe's mainstream parties. Instead, it appeared they came from other populists. The anti-Islam Party for Freedom (PVV) led by firebrand lawmaker Geert Wilders lost three of its four EU seats, according to the poll.

The pro-EU Groenlinks environmental party was also projected to win three seats, along with the center-right Christian Democratic Appeal (CDA). The pro-EU social liberal Democrats 66 (D66) and eurosceptic Christian Union - Reformed Political Party (CU-SGP) are projected to win two seats each, while mildly-eurosceptic pensioners' party 50PLUS and left-wing Socialist Party (SP) are also projected to win one seat each. The splintered result echoes Dutch domestic politics: There are 13 parties in the 150-seat national parliament.

Mainstream Dutch parties that support the EU took 70% of the vote, 3% more than they did five years ago, the Ipsos poll showed. Anti-EU parties slipped nearly 1% to 19%, according to the poll, which had a 2% margin of error.

The chaotic political situation in Britain may have influenced voters in the Netherlands, which is highly exposed economically to Brexit. Turnout hit a three-decade high for an EU election of 41%, up from 37% in 2014.

Baudet may have lost strong momentum in the final week of campaigning after publishing a book review that questioned whether women can both work and have children, and retweeting a video that was hosted by a German white supremacist group.

Political pundits cautioned not to read too much into the Dutch result, saying there may have been a domestic "Timmermans effect" that drew out supporters for a home-team candidate with a high profile.

The United Kingdom was the only other EU country to vote Thursday, even as the nation remained in political turmoil over its plans to leave the bloc altogether. No exit polls were expected Thursday night from the U.K. voting.

The elections come as support is surging for populists and nationalists who want to rein in the EU's powers and strictly limit immigration. Meanwhile, Europe's traditional political powerhouses, both conservative and left-wing, insist that unity is the best buffer against the shifting economic and security challenges posed by an emerging new world order.

But populists across several countries have united to challenge those centrist forces. On Saturday, Italy's anti-migrant Interior Minister Matteo Salvini of anti-immigrant League was joined at a rally by 10 other nationalist leaders, including far-right leaders Wilders, Marine Le Pen of France's National Rally party and Joerg Meuthen of the Alternative for Germany (AfD) party.

Wilders vowed to keep fighting the populist cause even after his party's projected big defeat.

"We had hoped for more seats," Wilders said in a statement. "But with one seat in the European Parliament we will, together with our European friends, fight even harder against the EU monster, Islam and mass-migration."

Pro-European leaders fear a good showing for the Eurosceptics will disrupt Brussels decision-making, threatening reform efforts at closer integration.

Salvini and Le Pen want their Europe of Nations and Freedom (ENF) group to become the third largest in Brussels. The League has topped opinion polls in Italy.

Le Pen wants to strike a blow to Emmanuel Macron's faltering French presidency by overtaking his centrist, pro-European party Republic on the Move. Polls give her RN party a slight edge, with around 23 percent support.

"Everything has changed," Le Pen told AFP.

"A whole range of political forces have risen up in spectacular fashion."

More than 400 million voters across Europe are electing 751 lawmakers, although that number is set to drop to 705 when Britain eventually leaves the EU. The U.K. has 73 European lawmakers, who would lose their jobs when their country completes its messy divorce from the EU. Some of its seats will be reassigned to other EU member states.

The British vote may have a direct impact on the future of embattled Prime Minister Theresa May, whose Conservative Party appears to be losing support amid a prolonged Brexit impasse. May has tried but failed for months to get lawmakers in the British Parliament to back her plan to leave the EU.

Both the Conservatives and Labour in Britain were predicted to be heading for an electoral pasting in Thursday's vote, due to the chaos over Brexit. Results of the vote will be announced Sunday night, and a poor showing for the Conservatives would increase the calls for May to step down as party leader, which would set in motion a leadership contest.

Britain's Brexit party, led by Nigel Farage, has appeared to gain strength in recent voter surveys and leading the latest opinion polls with 37 percent of the vote. Farage voted Thursday, then declared that he hopes to have the shortest possible tenure as a member of the European Parliament because he wants Britain to leave the EU as quickly as possible.

"If you want Brexit, you've got to vote Brexit," he said, warning lawmakers from Britain's two major parties — Conservatives and Labour — that they will be vanquished at Britain's next general election unless they respect voters' desire to leave the EU.

However, the pro-EU Liberal Democrats also look set to capitalize on the mixed Brexit messages of the main parties.

MPs have rejected May's withdrawal agreement and the country now finds itself electing lawmakers to an institution it plans to leave.

"We've been let down by both of the main parties," Rex Taylor, a 79-year-old retired professor, said as he voted in the Scottish city of Glasgow.

Voting in Britain was marred by the inability of hundreds of the 3 million EU citizens in Britain to vote despite having a legal right to do so. EU citizens who wanted to vote in Britain had to complete a form confirming they would not be voting in their homelands. Some say they did not receive the forms.

The Electoral Commission blamed the problem on the short notice that officials had to prepare for the election, which would not have been held in Britain if the country had left the EU in March, as planned.

However, Eurosceptics are not expected to sweep the whole bloc, with voters from Spain to Ireland and the former Soviet Baltic states indicating solid backing for the EU.

In Germany, surveys show Chancellor Angela Merkel's CDU party -- a heavyweight in the EU-wide centre-right EPP group -- in first place, with the Greens second.

The latest Eurobarometer survey commissioned by the European Parliament found 61 percent of respondents calling their country's EU membership a good thing -- the highest level since the early 1990s.

The polls will open on Friday in the Czech Republic and Ireland, and on Saturday in Latvia, Malta and Slovakia.

But most countries will be voting on Sunday, with the results expected overnight into Monday.

Juncker is stepping down after five years as president of the European Commission.

The hunt will also be on for someone to replace former Polish premier Donald Tusk as head of the EU council.