Unofficial results show that more than 60 percent of Bulgarians voted Sunday in favor of building a new nuclear power plant, but the voter turnout was far below the threshold needed to make the referendum binding.
The issue, which has been seen as a barometer of the relationship between the European Union's poorest member and Russia, appears likely to head to parliament, where the center-right ruling party plans to block the project.
The pro-Western government last March canceled a deal with Russia's Atomstroyexport for a 2,000-megawatt nuclear plant at the northern town of Belene, arguing that estimated costs of up to €10 billion ($13 billion) were too high.
The vote was called by the opposition Socialist party in an effort to force the government to reverse its decision. It was Bulgaria's first referendum since the fall of communism in 1989.
An unofficial vote count by the Alfa Research Agency showed that 21.8 percent of the 6.9 million eligible voters cast a ballot in the referendum, and 61 percent supported having a new nuclear plant. Official results were expected later this week.
The turnout appears well below the 60 percent needed to validate the vote, but if final results show it was above 20 percent and more than half of the votes were in favor, Parliament will have to review the issue within three months.
Prime Minister Boiko Borisov said Sunday that his ruling party, Citizens for the European Development of Bulgaria, will again block the project.
Analysts have linked the stance to the government's declared strategy of reducing the country's near-total dependence on Russian energy sources.
The Russian firm has filed a 1 billion-euro compensation claim at the Paris-based International Court of Arbitration.
The referendum has polarized Bulgarian public opinion along party lines and could affect general elections in July. Analysts anticipated that most voters Sunday would be hard-core supporters of each camp, producing the low turnout.