THE HAGUE — Harry van Bommel, a left-wing member of the Dutch Parliament, had persuasive allies in convincing voters that they should reject a trade pact with Ukraine — his special “Ukrainian team,” a gleefully contrarian group of émigrés whose sympathies lay with Russia.

They attended public meetings, appeared on television and used social media to denounce Ukraine’s pro-Western government as a bloodthirsty kleptocracy, unworthy of Dutch support. As Mr. Van Bommel recalled, it “was very handy to show that not all Ukrainians were in favor.”

Handy but also misleading: The most active members of the Ukrainian team were actually from Russia, or from Russian-speaking regions of Ukraine, and parroted the Kremlin line.

The Dutch referendum, held last April, became a battering ram aimed at the European Union. With turnout low, Dutch voters rejected the trade agreement between the European Union and Ukraine, delighting Moscow, emboldening pro-Russia populists around Europe and leaving political elites aghast.

It is unclear whether the Ukrainian team was directed by Russia or if it was acting out of shared sympathies, and Mr. Van Bommel said he never checked their identities. But Europe’s political establishment, already rattled by Britain’s vote to leave the European Union and the election of President Trump in the United States, is worried that the Netherlands referendum could foreshadow what is to come.

With elections slated for France, Germany and possibly Italy this year, officials across Europe are warning that the Russians are actively interfering, echoing the Central Intelligence Agency’s assertions that Moscow meddled in the United States presidential election.

Norway announced this month that Russia-linked hackers had attacked government ministries and a political party. Britain’s defense minister has accused Moscow of “weaponizing disinformation.” German, French and Italian officials have also accused Russia-linked partisans of meddling.

The Netherlands is holding its own national elections on March 15, and domestic intelligence officials say that foreign countries, notably Russia, have tried hundreds of times in recent months to penetrate the computers of government agencies and businesses. Volkskrant, a Dutch newspaper, reported last week that the same two Russian hacking groups that pilfered emails from the Democratic National Committee were among those targeting the Netherlands.

The Dutch interior minister announced that all vote tallies in the March election would be done by hand so as to remove computers from the electoral process and calm fears of hacking by unidentified “state actors.”

 

“Those in power are very worried — there is more than ample reason for alarm over interference in elections,” said Sijbren de Jong of the Hague Center for Strategic Studies, a research group in The Hague, the seat of the Dutch government. “But the real risk are populists who run, knowingly or unwittingly, with Russia’s agenda because they know it is damaging to the status quo in Europe that they want to destroy. All Russia really needs to do is sit back and let populists do their bidding.”

No one has yet come up with concrete evidence that the Russian state, rather than individual Russians, is working to skew the election, and many wonder why Moscow would even bother trying to do so in a small country with none of the geopolitical heft of the United States or Germany. But Mr. de Jong said the referendum last year showed that “a little effort goes a long way” and could help “destroy the European Union from inside.”