European antitrust regulators on Wednesday charged the Russian energy giant Gazprom with abusing its dominance in natural gas markets, a move amounting to a direct challenge to the authorities in Moscow. The European Commission, the European Union’s executive arm, said that unfair pricing might have resulted in higher gas prices in Bulgaria, Estonia, Latvia, Lithuania and Poland, which have long been wholly or substantially dependent on Russian gas. In those countries, the commission said, Gazprom was suspected of charging wholesalers prices that were significantly higher compared with the company’s costs or to benchmark prices.