Hundreds of Ukrainians protested Thursday against US energy giant Chevron's plans to explore for shale gas, seen as vital to the ex-Soviet country's plans to ease its energy dependence on Russia.

Chevron last year won a tender to explore the Olesky deposit in the west of the country, which the government estimates could hold 2.98 trillion cubic meters of gas.

But locals are concerned about the ecological consequences of shale gas exploration in the mountainous forest region, which is also a prominent tourist resort.

The action in Lviv, Ukraine's main western city, saw protesters chant "the price of gas is the health of our children," and "shale gas is the Chernobyl #2," a reference to the nuclear power plant disaster that struck Ukraine in 1986.

Activists also held up 66 chicken carcasses symbolising the number of local deputies who, despite protests, signed off on a production-sharing agreement between Ukraine and the US firm.

The deal is seen as a further step in Ukraine's drive to diversify its energy sources at a time when it is seeking closer relations with the European Union to break free from its dominant eastern neighbour Russia.

In January, Ukraine and the Anglo-Dutch group Shell signed a $10-billion production-sharing agreement to explore shale gas at the Yuzovska deposit in the eastern Donetsk region.