The Dutch government said on Wednesday it could not ignore the resounding "No" in a non-binding referendum on the European Union's association treaty with Ukraine, but that it may take weeks to decide how to respond.
Although the results were preliminary, they exposed dissatisfaction with the Dutch government and policy-making in Brussels - signalling a anti-establishment mood in a founding EU member weeks before Britain votes on membership.
There could also be far-reaching consequences for the fragile Dutch coalition government, which currently holds the rotating EU presidency and which has lost popularity amid a wave of anti-immigrant sentiment.
Exit polls indicated roughly 64 percent of Dutch voters voted "No" and 36 percent said "Yes". Although turnout was too close to call, early tallies indicated it was just ahead of a turnout minimum of 30 percent required for the vote to be valid.
"It's clear that 'No' have won by an overwhelming margin, the question is only if turnout is sufficient," Dutch Prime Minister Mark Rutte said in a televised reaction.
"If the turnout is above 30 percent with such a large margin of victory for the 'No' camp, then my sense is that ratification can't simply go ahead," Rutte added.