The referendum took place amid fears of vote meddling by Russia.

The two votes are seen as key tests of the former Soviet republic’s pro-European turn under Sandu, but have been overshadowed by accusations of Russian interference amid the war in neighbouring Ukraine.

“Moldova has faced an unprecedented assault on our country’s freedom and democracy, both today and in recent months,” Sandu told reporters in Chisinau.

She blamed “criminal groups, working together with foreign forces hostile to our national interests”, adding: “Their objective was to undermine a democratic process.”

In the referendum, with 90% of the vote counted, 54% had said “no” and 46% said “yes”, but the results could yet change as votes from abroad are counted.

In the presidential election, also held Sunday, Sandu gained 38% of the votes, according to the partial results. She is likely to face her closest competitor Alexandr Stoianoglo in a second round next month.

Stoianoglo, a former prosecutor backed by the pro-Russian Socialists picked up a higher-than-expected result of more than 28%.

Fears of Russian interference have been looming large after police made hundreds of arrests in recent weeks.

They acted after discovering an “unprecedented” vote-buying scheme they say could taint up to a quarter of the ballots cast in the country of 2.6 million.

Moscow has “categorically” rejected accusations of meddling.