Moldovans have cast their ballots in a presidential election that could prove pivotal for the country’s European future, amid accusations of Russian interference.

The pro-western incumbent, Maia Sandu, who has intensified the nation’s efforts to break away from Moscow’s influence, is facing the Kremlin-friendly political newcomer, Alexandr Stoianoglo from the Socialist party, in the second round of voting on Sunday.

The election in this small nation of under 3 million people in south-eastern Europe came two weeks after a key referendum in which a slim majority voted in favour of pursuing membership of the EU.

After casting her ballot in the capital of Chișinău, Sandu said: “Today, more than ever, we must be united, keep our peace, keep our vote, keep our independence.”

“Thieves want to buy our vote, thieves want to buy our country but the power of the people is infinitely greater,” she told reporters.

Since the breakup of the Soviet Union, Moldova has gravitated between pro-western and pro-Russian courses. But under Sandu, a former World Bank adviser, the impoverished country has accelerated its push to escape Moscow’s orbit as its war in neighbouring Ukraine continues.

Sandu’s team has intensified efforts to prevent a repeat of what it described as a large-scale vote-buying scheme orchestrated by Russian-backed fugitive oligarch Ilan Shor during the first round and the EU aspirations referendum on 20 October.

Officials believe that Moscow invested approximately $100m (£77.2m) before the first vote and had reportedly smuggled in some of the funds by “money mules” detained by police at the main airport while carrying bundles of €10,000 (£8,390) in cash.

“Moldova has had a monumental task before it: just two weeks to stop a sprawling Kremlin-backed vote-buying scheme that proved effective in the twin vote on 20 October,” said Olga Rosca, a foreign policy adviser to Sandu.

Still, on Sunday, Sandu’s national security adviser, Stanislav Secrieru, wrote on X that they were “seeing massive interference by Russia in our electoral process … an effort with high potential to distort the outcome.”

“Cybersecurity agency reports the Central Election Commission’s voter education site was temporarily down this morning due to a DDoS attack,” Secrieru added.

The Kremlin has denied interfering in the vote.

“We resolutely reject any accusations that we are somehow interfering in this. We are not doing this,” Kremlin spokesperson Dmitry Peskov said.

The tight result of the EU referendum has weakened Sandu’s standing, placing her in direct opposition to former prosecutor general Stoianoglo, who exceeded expectations with 26% of the vote on the Party of Socialists’ ticket.

Sandu is relying on the sizeable Moldovan diaspora – about 20% of the electorate – that traditionally backs pro-EU candidates to help secure her victory.

Moldova’s diaspora played a key role in a nationwide referendum when a narrow majority of 50.35% voted to secure Moldova’s path toward EU membership

In last weekend’s presidential debate, Sandu accused Stoianoglo of being a “Trojan horse” candidate for outside interests bent on seizing control of Moldova.

Stoianoglo has denied working on behalf of Russia. In an interview with the Guardian in October, he claimed that he was in favour of joining the EU but boycotted the vote, calling it a parody.

He has also declined to criticise the Kremlin for its invasion of Ukraine and called for improved relations with Moscow. “The level of Russian interference in Moldova is highly exaggerated,” he said, adding that he would seek a “reset of relations” with Moscow.

Russia’s invasion of Ukraine has shocked many in Chișinău, which is just a few hours’ drive from Ukraine’s Black Sea port city of Odesa, and the Kremlin’s shadow looms large. Moscow has 1,500 troops stationed in Transnistria, a region run by pro-Russian separatists who broke away from Moldova’s government in a brief war in the 1990s.

The election outcome will be closely watched in Brussels a week after Georgia, another ex-Soviet state hoping to join the EU, re-elected a party viewed by most countries as increasingly Moscow-friendly and authoritarian.