Russia's state-run natural gas monopoly Gazprom has reduced gas supplies to Europe in efforts to conserve domestic supplies in the face of bitter cold temperatures at home.
Gazprom officials say the cuts are a temporary measure in response to increased consumption after the cold spell struck western Russia.
Hungary, Ukraine and Italy have confirmed the reductions. Ukrainian Energy Minister Ivan Plachkov says his country agreed with Russia to cut gas transit to Europe by 40 million cubic meters a day.
Much of Russia's European gas exports reach their destinations via Ukrainian pipelines.
In Moscow, at least one person froze to death overnight, as temperatures plunged to minus-30 degrees below zero (Centigrade). Russian news agencies say 22 other people have died from the cold in surrounding regions.