Gazprom says it is cutting daily gas deliveries to Europe via the Nord Stream pipeline to about 20 percent of its capacity from Wednesday.
The cut marks Russia’s latest blow to European countries over their support for Ukraine.
The company said it was halting supplies through its single biggest gas link to Germany due to the "technical condition of the engine".
As a result, flows through the Nord Stream 1 pipeline would fall to 33 million cubic meters per day from Wednesday, it said.
That is half of the current flows, which are already only 40% of normal capacity. Prior to the war Europe imported about 40% of its gas and 30% of its oil from Russia.
The Kremlin says the gas disruption is the result of maintenance issues and Western sanctions. Germany said it saw no technical reason for the latest reduction.
Ukrainian President Volodymyr Zelensky accused Russia of waging a “gas war”, calling on Europe to retaliate by boosting its sanctions against Moscow.
Europe is heavily dependent on Russian energy resources, and the West accuses Moscow of using energy as a weapon in retaliation for its sanctions.
Gazprom’s announcement came after Russia last week restored critical gas supplies to Europe through Germany via Nord Stream after 10 days of maintenance, but only at 40 percent of the pipeline’s capacity.
Politicians in Europe have repeatedly warned Russia could cut off gas this winter, a step that would thrust Germany into recession and lead to soaring prices for consumers already faced with painfully high energy costs. The Kremlin has said Moscow is not interested in a complete stoppage of gas supplies to Europe.
Rising energy prices and a global wheat shortage are among the most far-reaching effects of the Ukraine conflict.
They have caused a cost of living crisis in Europe amid rising inflation, leading to growing dissatisfaction.