Viktor Yushchenko, the Ukrainian president, has demanded that Russia resume gas shipments to Europe "immediately" after supplies were halted following the debt row and accusations of theft.
The president wrote to Dmitry Medvedev, the Russian president, and Jose Manuel Barroso, the European Commission head, on Wednesday to protest against the cut.
Valentyn Zemlyansky, a spokesman for Naftogaz, Ukraine's state energy company, said Gazprom, Russia's state gas company, had stopped sending gas to European consumers at 0744 local time (0544 GMT).
"Words fail us," he said.
However, Alexander Medvedev, the vice-president of Gazprom, blamed Ukraine for the cut in gas deliveries to Europe.
"Last night Ukraine shut down all gas pipelines to Europe. This morning no pipeline is bringing gas through Ukraine to Europe," he said.
Neave Barker, Al Jazeera's correspondent in Moscow, said it was difficult to determine who was telling the truth to the European Union, who are watching their gas supplies dwindle.
"This is political and economic tit-for-tat. It appears as if any last-minute attempts to broker a deal between Kiev and Moscow have failed," he said.
EU countries, which are experiencing sub-zero temperatures in some areas, receive about 80 per cent of Russian gas exports through Ukraine.
|Alexei Miller, Gazprom's CEO, is to fly to Brussels for talks with European officials [EPA]
On Wednesday, 10 European countries reported a complete halt in Russian supplies, including Austria, the Czech Republic, Romania and Slovakia.
Medvedev said he would fly to Brussels with Alexei Miller, Gazprom's chief executive, for talks with European officials on Thursday.
"They will be high-level talks with the European Commission and European parliament," he said.
The European Commission also proposed on Wednesday sending observers to Ukraine to measure the flow of natural gas arriving from Russia, a spokesman said.
European industrial and agricultural users, which consume thousands of cubic metres per hour, will be primarily effected by the cuts.
The Croatian finance ministry said reductions had already started for big industrial consumers.
Lubomir Jahnatek, the Slovakian finance minister said on Tuesday: "Gas supplies to selected wholesale buyers may fall, but we will do our best to spare households, hospitals and schools."