Demonstrators marched on Sofia to call on the government to ban shale gas exploration in the country. Protesters carried signs warning of potential environmental damage from shale gas exploration. Demonstrators pointed to a ban on shale gas production in France as a regional model, the Sofia New Agency reported.
Sofia in June passed a deal with U.S. supremajor Chevron to explore the shale gas potential in the country's northeast.
Shale gas is emerging as a key natural resource in countries like the United States and Poland. Extraction methods, known as fracking, are controversial because of the fear of groundwater contamination.
Bulgarian Energy Minister Traicho Traikov said there is potentially enough shale gas in his country to meet domestic demand for the next millennium.
The Novi Pazar shale gas deposit in Bulgaria holds an estimated 1.05 trillion-35 trillion cubic feet of natural gas deposits.