European Union antitrust regulators charged Russian gas giant Gazprom on Wednesday with abusing its dominant position in Poland, Hungary and six other countries in Eastern Europe following more than two years of investigation.

The European Commission said the state-controlled company, a vital supplier of energy to Europe despite frequent political disputes, had hindered cross-border competition across the region and overcharged in five of the countries.

“We find that it (Gazprom) may have built artificial barriers preventing gas from flowing from certain Central Eastern European countries to others, hindering cross-border competition,” European Competition Commissioner Margrethe Vestager said in a statement.

“Keeping national gas markets separate also allowed Gazprom to charge prices that we at this stage consider to be unfair,” she said.

Her decision to move against Gazprom came more than two years after Brussels started investigating the gas group and just a week after she ch