Bulgarians' hopes that Russia's Lukoil, owner of the country's only oil refinery, may agree to extend the one-month freeze on retail fuel prices, which expired during the Easter holidays, have proved unrealistic.

On a day when Sofia saw several hundred drivers protest against the spike in fuel prices, with smaller rallies in other Bulgarian cities, Lukoil Bulgaria increased the wholesale prices, which led to immediate hikes at the gas stations.

The most widely used fuel A 95 is selling at BGN 2.34 per liter (up from BGN 2.28) as of Thursday morning.

At the end of March Bulgaria's center-right government convinced Lukoil Bulgaria to place a one-month moratorium on the increase of its gas and diesel prices as part of efforts to tame the spike in petrol costs, linked to the increase in global crude oil prices.

The agreement was reached after car marches across the country protested against recent fuel price hike.

The moratorium expired on April 23, Saturday. It was in force for only 29% of the retail fuel market, which is the share held by Lukoil Bulgaria gas stations.

The moratorium has fueled suspicions of very close ties between Bulgaria's Prime Minister Boyko Borisov and the head of Lukoil Bulgaria Valentin Zlatev, whom the opposition has described as "the country's back seat ruler" and "the oil oligarch, who pulls the strings of the government".