Poland's anti-monopoly watchdog said on Wednesday it had fined Russia's Gazprom more than 29 billion zlotys ($7.6 billion) for building the Nord Stream 2 gas pipeline without its approval.
The UOKiK watchdog also said it had imposed a 234 million zloty fine on five other firms involved in financing $11 billion project set to double Russia's gas export capacity via the Baltic Sea.
Nord Stream 2 is led by Gazprom, with half of the funding provided by Germany's Uniper and BASF's Wintershall unit, Anglo-Dutch company Shell, Austria's OMV and Engie.
Poland sees Nord Stream 2 as a threat to Europe's energy security as it will increase reliance on Russian energy.
The United States has also imposed sanctions on companies laying pipes for the project.
UOKiK has been examining the project for years. In August it fined Gazprom 213 million zlotys over a lack of cooperation regarding the project.
"The launch of NS2 will threaten the continuity of natural gas supplies to Poland. An increase in the price of the product is also highly likely, with the said increase being borne by Polish consumers," said Tomasz Chrostny, president of UOKiK.
"Completion of this investment project increases economic dependence on Russian gas - not only in the case of Poland, but also of other European states," Chrostny said.
Gazprom did not reply to a request for immediate comment.
Construction of the 1,230-kilometre pipeline is nearly finished but for a final stretch of roughly 120 km in Danish waters.
Work was halted in December as pipe-laying company Swiss-Dutch Allseas suspended operations because of the US sanctions targeting companies providing vessels.
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