Bulgaria's government has defended its decision to impose a new tax on Russian gas transiting through the country as Hungary and Serbia -- which rely on supplies from Moscow -- vowed to respond to the move, which they called a “hostile” step. Bulgaria imposed a tax on Russian gas transit in the amount of 20 leva ($10.80) per megawatt-hour last week, prompting reactions in Budapest and Belgrade, which receive Russian gas through Bulgaria. Bulgarian Prime Minister Nikolay Denkov on October 18 defended the move, saying that “there…