Eastbound natural gas flows via the Yamal-Europe pipeline halved on Thursday morning on their way to Poland - the same day that Moscow ordered forces to invade Ukraine.
It was not immediately clear whether the lower flows were related to the developments in Ukraine, another major route for Russian gas exports to Europe. Russian state gas company Gazprom declined immediate comment.
The pipeline between Poland and Germany usually accounts for about 15 percent of Russia’s westbound supply of gas to Europe and Turkey but since December has been operating in reverse, driving European gas price rises.
Russian forces fired missiles at several Ukrainian cities and landed troops on its south coast on Thursday, officials and media said, after President Vladimir Putin authorized what he called a special military operation in the east.
Earlier this week Putin said that Russia would continue to supply gas to world markets.
Flows through the Yamal-Europe pipeline continued to move in reverse mode for a tenth week, data from German network operator Gascade showed.
Flows from Germany to Poland via the Mallnow metering point were at 680,000 kilowatt hours per hour (kWh/h) on Thursday, halving from 1.5 million kWh/h on Wednesday.
Renominations, or bids, to flow gas from Germany to Poland are also expected at about 700,000 kWh/h until Friday morning.
Russian gas export monopoly Gazprom, which can book pipeline capacity at daily auctions, has not ordered any transit capacity for February and March via the route.
It did not book capacity for the second and third quarters of the year and has no plans to hold spot gas sales at its electronic platform this week.
On another major route for Russian deliveries to Europe, for supply to Slovakia from Ukraine via the Velke Kapusany border point, capacity nominations for Thursday stood at 622,477 MWh. That was nearly double the levels seen in recent days and the highest daily nomination since February 7.