Thousands of protesters across Romania rallied against Chevron's plans to tap the country's shale resources, demanding the government withdraw concessions and forbid the US supermajor to drill its first test wells.
Nearly 1000 people protested in the eastern border town of Barlad, where Chevron holds 1.6 million acre concession. Some were wearing gas masks and many were chanting "Chevron go home", according to a Reuters report.
Another 300 protesters gathered in Bucharest's University Square, according to AFP.
Concerns about technologies such as hydraulic fracturing used to exploit shale gas have found a voice across Europe, where the population is denser and environmental restrictions tighter compared to the US, the home of the modern shale boom.
Many fear that potential consequences of fracking outweigh the benefits of energy independence that a European shale boom might bring. The oil and gas industry maintains that fracking can be done safely and poses no inherent risk to local communities - assertions backed up by many experts.
Analysts say Romania's shale-gas deposits could help make the Balkan nation self-reliant in gas use. Protesters on Thursday said that prospect is not worth the risk.
"Shale ... will only wreak havoc here," 63-year-old pensioner Elena Arsenie told Reuters.
Over the past weeks, Romanian Prime Minister Victor Ponta has softened his views on shale gas since a parliamentary election in December, which earned his ruling leftist alliance an overwhelming two-thirds majority in parliament.
But analysts say if public opposition heightens further, authorities might need to reconsider their stance on shale for fear of alienating millions of voters, a move that could potentially prevent Chevron from setting up one of its biggest operations.
Chevron has exploration rights for three blocks of 670,000 acres near the Black Sea, in addition to the concession near Barlad.
The company said in a statement on Thursday that it would only produce gas from shale using what it said were safe and proven technologies.
"Chevron respects that individuals have the right to voice their opinions ... We recognise the importance of informing the public about the technologies employed in the prospecting phase, technologies which are commonly used in the conventional oil and gas industry," Chevron spokeswoman Sally Jones said, according to Reuters.
She said Chevron will only carry out prospecting activities this year and did not plan to fracture any wells.
The US Energy Information Administration estimates Romania and neighbouring Bulgaria and Hungary could have 538 billion cubic metres of shale gas between them, slightly more than Europe's annual consumption and enough to cover Romania's needs for almost 40 years.