WARSAW—Poland’s anti-monopoly office UOKiK said on Oct. 7 it has fined Gazprom over 29 billion zlotys ($7.61 billion) for building the Nord Stream 2 pipeline without the watchdog’s approval.

UOKiK has also imposed a 234 million zloty fine on the remaining five companies financing the pipeline, which would 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.