PISAREVKA, Russia - Russian natural gas began flowing into Europe on Tuesday after a nearly two-week cutoff that left large parts of the continent shivering and underscored its vulnerability and dependence on Russia's energy.

But a higher price Ukraine now has to pay for the Russian gas will further cripple an economy badly hurt by the financial crisis and could set the stage for another gas dispute with Russia. The office of Ukraine's president has already criticized the deal, saying it hurt the country's interests.

Russia's gas monopoly Gazprom began pumping gas into Ukraine at around 10:30 a.m. Moscow time, spokesman Boris Sapozhnikov said by telephone from the Sudzha metering station on the border with Ukraine. Ukraine's Naftogaz state gas company confirmed gas flowed through Sudzha, Pisarevka and other gas metering stations on the border.

Several hours later, Slovak Economics Minister Lubomir Jahnatek said his country started receiving the Russian gas. It could take longer for other European customers to begin receiving the Russian gas via Ukraine, which is the size of France, and reach European customers. Europe gets about a fifth of its natural gas from Russia.

Russia halted the supplies Jan. 7 as it argued with Ukraine over 2009 gas prices and allegations that Ukraine was stealing gas destined for Europe.

More than 15 countries in the Balkans and eastern Europe were left scrambling for alternative energy sources; factories shut and millions of people shivered in unheated homes. Bulgaria and Slovakia, in particular, rely almost entirely on Russia for gas.

European Commission president Jose Manuel Barroso hailed the resumption of supplies, but added that "it is difficult to welcome something that should not have happened in the first place."

"It was utterly unacceptable that European gas consumers were held hostage to this dispute between Russia and Ukraine," he said. "We must not allow ourselves to be placed in this position in future. New year is for fireworks and celebration, not gas crises."

Barroso said that Europe must learn the lessons of the dispute and diversify its energy sources and supply routes. "This painful episode is a sharp reminder that the EU needs to take energy security seriously," he said in a statement.

The gas dispute had been complicated by geopolitical struggles over Ukraine's future and over lucrative export routes for the energy riches of the former Soviet Union.

Ukrainian President Viktor Yushchenko has accused Russia of using the gas dispute to destabilize his country and acquire control of its strategic pipeline system. The Ukrainian Foreign Ministry said Tuesday that Russia had mounted a "planned gas attack" aimed at quashing Ukraine's independence.

The new agreement, brokered by Russia's Prime Minister Vladimir Putin and his Ukrainian counterpart Yulia Tymoshenko, calls for Ukraine to receive gas at a 20 per cent discount from this year's average European price, which Russia says is $450 per 1,000 cubic metres.

Gazprom said Ukraine will pay $360 per 1,000 cubic metres of Russian gas in the first quarter -- compared with last year's price of $179.5 -- and prices will be revised on a quarterly basis.

European gas prices are expected to fall sharply this year, due to the reduction in oil prices. By midsummer, Ukraine could be paying as little as $150 for 1,000 cubic metres, said Ronald Smith, a strategist at Moscow's Alfa Bank.