"That is all they are sending, in several hours Europe will feel it," Zemlyansky told The Associated Press.
Gazprom officials could not be immediately reached for comment and the drop in supplies could not be immediately confirmed.
Gazprom said late Monday that it would cut the amount of gas it ships to Europe through Ukraine by 65.3 million cubic meters - the same amount it accuses Ukraine of having stolen when it ran through its pipelines.
Kiev denied the accusations, saying Russia is to blame for the disruption because it is refusing to ship extra gas used to make the delivery.
The statement is bad news for European consumers.
Some European countries are already experiencing supply problems after Russia cut off supplies to its neighbor on Jan. 1 over pricing disagreements and outstanding debt. Hungary, Romania and Bulgaria say supplies from pipelines through Ukraine remained down, in Romania's case by 30 percent.
The reductions come as a European Union commission was to meet with senior Ukrainian officials Tuesday to discuss the crisis.
Russia's reductions appear aimed at putting pressure on Ukraine, which has turned down several offers on prices and transit fees by Gazprom and which has enough gas reservers to last for weeks without Russian gas.
During a similar dispute between Ukraine and Russia in 2006, several West European countries saw their gas supplies drop by 30 percent or more. This time Gazprom's customers were better prepared, having built up substantial reserves.
Although the previous gas cutoff was seen as punishment for Ukraine's pro-Western policies, this time Gazprom is insisting it is a commercial dispute. Both countries are seeking to prove they are a reliable energy partner for the European Union.
