Russian gas monopoly Gazprom said it cut all gas supplies to Ukraine yesterday after talks broke down over payments for past shipments and a price for 2009.
Gazprom spokesman Igor Volobuyev said the cuts began as planned at 10am (0700 GMT).
A spokesman for Ukrainian gas company Naftogaz confirmed a steady drop in supplies.
There are fears that a cut-off could lead to a repetition of the January 2006 gas crisis. Then, a similar dispute between Russia and Ukraine briefly interrupted gas shipments to many European countries. Ukraine controls the pipelines through which Russia supplies most of its customers in Europe.
While cutting gas to Ukraine, Gazprom said it has increased the gas pumped through pipelines that mainly serve Europe, which gets about a quarter of its gas from Russia.
Russian Prime Minister Vladimir Putin has warned Ukraine against diverting gas intended for other customers, saying that could have “quite serious consequences for the transit country itself” by damaging relations with Europe.
Ukraine’s president and prime minister issued a statement saying they would guarantee the uninterrupted transit of natural gas through Ukrainian territory to Europe.
The cut-off comes as Europe approaches the depths of winter. Naftogaz director Oleh Dubina has said Ukraine has enough gas in reserve to last it through to early April.
The deadlock over gas supplies reflects the deep political split between Moscow and Kiev.
Ukrainian President Viktor Yushchenko has angered the Kremlin through his efforts to build ties to Western Europe and his support of Georgia in its August war with Russia.
Ukraine’s position in the dispute is further complicated by divisions in the country’s leadership. Mr Yushchenko and Prime Minister Yulia Tymoshenko, bitter political rivals, are at odds over gas policy and relations with Russia, among other issues.
Gazprom had warned it would cut gas supplies unless Ukraine paid off all of its debts and signed a deal setting prices for 2009 deliveries by midnight. Neither was done.
Naftogaz paid $1.5billion to the Swiss-based gas trader Rosukrenergo, which it says covers the debt. But Gazprom CEO Alexei Miller said it had not yet received the money.
The other stumbling block was the failure to sign a contract for 2009 gas deliveries.