Russia's Gazprom state gas monopoly on Tuesday resumed pumping supplies to Europe via Ukraine after a six-day cutoff, a company spokesman said.
The company turned on the taps after 10 am Moscow times (0700 GMT), said Gazprom spokesman Boris Sapozhnikov at Sudzha gas metering station on the border with Ukraine.
Russian and European Union officials said it would take at least a day for gas to reach consumers in Europe after the first gas is pumped into Ukraine.
Russia had accused Ukraine of stealing gas intended for Europe and only restarted supplies after an EU-led monitoring mission was deployed to the Ukrainian territory to track gas flow. Ukraine fiercely denied the siphoning charge, but Prime Minister Yulia Tymoshenko warned Monday Ukraine will have to use some gas from Russia as so-called "technical gas" to power compressors that push Europe-bound gas through the pipelines.
Gazprom has insisted it's Ukraine's duty to provide the gas, setting the stage for more bickering and possible supply interruptions.
Russia's President Dmitry Medvedev has ordered Gazprom to reduce supplies if it again sees Ukraine siphoning gas, and suspend it completely if it believes Ukraine continuously steals gas. Ukraine's position potentially "creates a crisis situation with the transit of Russian gas to European users," Gazprom spokesman Sergei Kupriyanov said in a statement late Monday.
The gas cutoff has affected more than 15 countries, with Bosnia, Bulgaria, the Czech Republic, Hungary, Serbia and Slovakia among the worst hit. Sales of electric heaters have soared and thousands of businesses in eastern Europe have been forced to cut production or even shut down.