A major Austrian natural-gas company, OMV, said in a statement that "around a third of the volume has been cut."
Hungary's leading energy group, MOL, said it had noted a 40 percent drop in gas pressure at its border with Ukraine. As a result, it said it would cut gas transit to Serbia and Bosnia-Herzegovina by a similar rate.
Other countries also noticed a drop in gas deliveries. Croatia and Slovakia reported a 30 percent shortfall, and Romanian Economy Minster Codrut Seres said his country has experienced a drop of 5 million cubic meters a day.
Russia's state-owned gas company Gazprom cut supplies to Ukraine yesterday in a price dispute.
Ukrainian authorities have denied Russian charges that Kyiv has started to illegally siphon away gas flowing through pipelines in Ukraine for European users -- although Kyiv said today it might be forced to do so if temperatures drop well below freezing.