The Moldovan diaspora will hold a critical role in Sunday’s high-stakes parliamentary elections as the country battles against an unprecedented Russian vote-buying operation to try to unseat the incumbent pro-European party, said the former deputy prime minister.

Civilian foreign interference watchdogs say Russia is flooding the overseas voter communities with cash, including one advertising campaign offering people €500 to be election observers in the EU with the lure of “bonuses of up to €30,000” for evidence of voter fraud.

“They are basically incentivising people to report any type of violation in exchange for money. We think that it might be a preparation to say the election was rigged,” Victoria Olari, a researcher at the Atlantic Council’s Digital Forensic Research Lab in Chișinǎu, said.

Moldova is considered highly vulnerable to any Russian expansion, bordering Ukraine and with a diverse population including pro-Russian voters.

“It is a huge operation, it is something that has not happened in any other country. They are spending crazy money,” said Valeriu Pașa, a senior analyst and founder of WatchDog, another civil society monitor.

Earlier this week the president, Maia Sandu, warned that the independence of Moldova, a country of just 2.7 million people, was in danger after police arrested dozens of people accused of being in a Russia-backed plot to cause violence on the streets.

She has called it the “most consequential” election in the small country’s history, as it teeters between its powerful neighbour Russia and the EU, to which it is an accession candidate.

Election experts say diaspora voters are being targeted because they played a fundamental role in last November’s presidential elections, responsible for as much as 19% of the ballot.

Nicu Popescu, a candidate for the ruling Party of Action and Solidarity (PAS) and former deputy prime minister under Sandu, said disinformation was only part of the battle. Buying votes, he said, was “cheaper than missiles”.

“The digital part, the disinformation, is about a third of their operation, but the biggest chunk of it is cash, either cryptocurrency or bank transfers. It is a massive, brutal, direct vote-buying scheme targeting online manipulators, party activists, journalists and influencers.

“It is also clear that the EU diaspora has always been voting pro-EU, so the Russians have been trying to also derail that,” he said. However, he cautioned that the Russian goal was not to swing pro-European voters but to ensure “hesitant pro-Russian voters turn out”.

Fears of interference on Sunday were further fuelled on Friday after Serbian police arrested two people accused of running “combat tactical training” for dozens of protesters before Sunday’s ballot.

Sandu won a second term in office last November after tense elections with 30 to 40 fake bomb alerts across overseas polling stations.

“The diaspora will be crucial, because they are one of the highest proportions of voters in democratic elections across the world. This diaspora has always voted in a strongly pro-European manner, so it will be fundamental to the outcome,” said Popescu.

Olari said the aim of the Russians was not necessarily to get pro-Russian parties elected but to shift support away from pro-European parties and sow seeds of doubt.

“We saw that in Romania over two election cycles they went from pro-industrial west and pro-European to a situation where more are supporting the far right and pro-Russian groups,” she said.

Pașa, who has also identified attempts to buy election observers overseas, said he did not think the “independent observers” would be “trapped” into committing fraud themselves, but they were being asked to take videos and report back every two hours.

“I think the Russians really believe that they can find frauds, that they can find substantial differences between the numbers reported by the [Moldovan] Central Electoral Commission and by their observers. They do not believe in democracy. They cannot trust that hundreds of thousands of people will spend hours waiting to vote or travel hundreds of kilometres to take part in a democratic process.”