Thousands took to the streets of Romania on Sunday to protest against plans by US energy giant Chevron to drill for shale gas. "Chevron US, you can't just drop in uninvited and leave death in your wake", read some banners in Bucharest where hundreds of people gathered in the capital's University square. Similar protests were held in dozens of towns and cities across Romania. "Hydraulic fractures never heal", said protesters referring to the highly controversial drilling method used to unlock shale gas, called hydraulic fracturing or "fracking". "We have seen the effects of fracking on the environment in the US and we do not want the same to happen here", Alexandra Paslaru, a student said. The technique consists of pumping water and chemicals at high pressure into deep rock formations to free oil and gas, but critics point to studies that show fracking increases the risk of contaminating drinking water. Chevron has permits to explore for shale gas in northeastern Romania as well as on Romania's Black Sea coast. The company says it will abide by all environmental regulations. Despite local opposition, the company has started to build its first exploration well in the village of Pungesti. Protesters also lashed at the government of leftist Prime minister Victor Ponta. After fighting against shale gas while in opposition, Ponta is now a supporter of this new source of energy.