Moldova’s pro-EU President Maia Sandu has claimed a second term after a tense election run-off seen as a choice between Europe and Russia.

With most votes counted Sandu had won 55%, and in a late-night speech she promised to be president for all Moldovans.

Her rival Alexandr Stoianoglo, who was backed by the pro-Russian Party of Socialists, had called for a closer relationship with Moscow.

During the day the president’s national security adviser said there had been “massive interference” from Russia in Moldova’s electoral process that had “high potential to distort the outcome”.

Russia had already denied meddling in the vote, which came a week after another key Eastern European election in Georgia, whose president said it had been a “Russian special operation”.

Stoianoglo, who was fired as prosecutor general by Sandu, has denied being pro-Kremlin.

As polls closed, both Maia Sandu, 52, and her rival thanked voters, with Stoianoglo speaking in Russian as well as Romanian. Although Romanian is Moldova’s main language, Russian is widely spoken because of its Soviet past.

Turnout at 54% was high, especially among expat voters at polling stations abroad.

Stoianoglo took an initial lead on the night and was the more successful candidate in Moldova itself with more than 51% of the vote. Sandu won in the capital Chisinau, and she was completely dominant among expat voters.

As she overtook her challenger late on Sunday night, there was cheering at her campaign headquarters and chants of “victory”.

In a hoarse voice she praised her compatriots for saving Moldova and giving “a lesson in democracy, worthy of being written in history books”.

Then, moving into Russian, she said: “I have heard your voice – both those who supported me and those who voted for Mr. Stoianoglo. In our choice for a dignified future, no-one lost… we need to stand united.”

Maia Sandu’s foreign policy adviser, Olga Rosca, told the BBC she was proud of the result.

Asked whether she was surprised that Stoianoglo had won in Moldova itself, she said the vote in Moldova and abroad should be seen as one and the same: “We never divide people into Moldovans at home and expatriates – we see Moldovans as one family.”

With elections coming next year she said the president had “clearly indicated she has heard the mood for change. On several occasions between the [two presidential] votes she said the fight against corruption must be intensified and justice reform must be accelerated – she’s committed to this work”.

The final result will be declared on Monday.

EU Commission President Ursula von der Leyen congratulated Sandu, saying “it takes a rare kind of strength to overcome the challenges you’ve faced in this election.

“I’m glad to continue working with you towards a European future for Moldova and its people,” her message on X said.

Casting his ballot, Alexandr Stoianoglo had promised to be an “apolitical president”, and that he had voted for “a Moldova that should develop in harmony with both the West and the East”.

Stoianoglo polled particularly well in rural areas and the south, while Sandu was ahead in the cities and with young voters.

After casting her ballot, Sandu had warned of “thieves” who sought to buy their vote and their country.

Presidential national security adviser Stanislav Secrieru said Russia had organised buses and large charter flights to bring voters to polling stations.

Bomb scares had briefly disrupted voting in Moldova, at UK polling stations in Liverpool and Northampton and at Frankfurt and Kaiserslautern in Germany, he added.

A Soviet republic for 51 years, Moldova is flanked by Ukraine and Romania and one of Europe’s poorest countries. It has a population of 2.5 million and an expat population of 1.2 million.

Moldova’s authorities have long warned that a fugitive oligarch called Ilan Shor has spent $39m (£30m) trying to buy the election for Moscow with handouts to 138,000 Moldovans.

Shor, who is based in Moscow, denies wrongdoing but did promise cash payments to anyone prepared to back his call for a “firm No” to the EU.

Commentators and politicians had warned that a Stoianoglo victory could radically change the political landscape in the Danube and Black Sea region, not because he was some kind of “Trojan horse”, but rather because Russia has thrown its weight behind him.

There were queues at polling stations in Moscow, Italy and among voters from a mainly Russian-speaking breakaway region of Transnistria, who had to cross the River Dniester into Moldovan-controlled territory to vote. Transnistria is home to a Russian military base and a huge arms depot.

Moldova’s election commission said it was aware of reports of organised and illegal transports of voters by air and land in Russia, Belarus, Azerbaijan and Turkey, and appealed to the public to report further violations.

Although Sandu had easily won the first round of the vote, several candidates swung behind Stoianoglo, although the third-placed candidate refused to back either of the two.

The first round coincided with a nail-biting referendum on backing a change to the constitution embracing the commitment to join the EU.

In the end the vote passed by a tiny margin in favour, and Maia Sandu said there had been clear evidence of attempts to buy 300,000 votes.