The consortium in charge of a twin pipeline system carrying Russian natural gas through the Baltic Sea said it was finished with routine annual maintenance.

"Regular maintenance works are an essential part of Nord Stream's long-term pipeline integrity management strategy to ensure that the pipelines will be able to continue transporting up to 1.9 trillion cubic feet of gas per year safely and efficiently for at least 50 years," the pipeline consortium said in a statement. "The works included annual maintenance of mechanical components, as well as testing of the automation system."

Pipeline consortium Nord Stream AG, which has its headquarters in Switzerland, said the maintenance period stretched from Aug. 11 to Thursday. The scheduled outage was coordinated in advance and the consortium said supply interruptions were anticipated by downstream European consumers ahead of time.

The first leg of the pipeline system went into service in 2011. British energy company BP a year after the pipeline went into service said it was considering linking the Nord Stream natural gas pipeline to British ports.

Gazprom Chief Executive Officer Alexei Miller said in July new lines along what he said was the shortest link between northern Russia and the European market are less than five years off.

Gazprom officials met in early June with representatives from Austrian energy company OMV, a member of the Nord Stream pipeline consortium. Both sides signed a memorandum of understanding to examine the possible construction of two additional lines to the existing Nord Stream network.