US energy company Chevron has resumed its search for shale gas at a controversial site in north-east Romania after hundreds of riot police forcefully removed protesters from the village of Pungesti.

For more than two months, the village, which is believed to be sitting on large reserves of the valuable natural resource, has been the site of largely peaceful protests. Villagers, many of whom are elderly farmers, have set up camp next to the fields targeted for drilling, spending their nights in makeshift tents and cooking on open fires.

Even as the weather turned and temperatures dropped below zero, they looked set to stick the winter out. "We want the mayor to leave and Chevron to leave. We need courageous men, not to use force, just to show them we are united and we are not afraid," said Alexandru Focșa, 45, a farmer who has been camping since October.

At 4am on Monday the Romanian gendarmerie [paramilitary police force] moved in to secure the way for Chevron's trucks. In a scene that resembled a military operation, they occupied the village, blocking all access points with riot police vans and preventing anyone from leaving or entering for over 24 hours. Several villagers were detained and fined for the criminal offence of blocking a public road. Villagers say that anyone leaving their homes was stopped for questioning.

With no journalists allowed entry at the time, details are vague. But local newspapers claim that between 30 and 40 people had been beaten by police. Many villagers complained of brutality and injustice. Costică Spiridon, 56, a former village mayor, said: "They came on Tuesday morning with their clubs, they shoved me, I fractured a rib."

By the time the police started to move out and the roads were opened up, Chevron had built a new access road, erected a metal fence around the drilling site and deployed their own private security team.

Prime minister, Victor Ponta, has responded to anti-fracking protests around the country by saying that "the actions of the gendarmes were 100% according to the law and I congratulate them for this."

But others are demanding investigation. Maria-Nicoleta Andreescu, executive director of the Helsinki Committee Association for the defence of human rights in Romania, said: "There are important signs that indicate that the gendarmes' actions were at least abusive if not illegal. It is very clear is that by restricting the access of the press in the area the authorities did not allow the public to be informed."

In response to questions from the Guardian, Chevron said: "The company is committed to building constructive and positive relationships with the communities where we operate and we will continue our dialogue with the public, local communities and authorities on our projects." Explaning this week's events, a spokesperson said they are "committed to working with local communities to explain the benefits of natural gas."

• Additional reporting by Stefan Mako