The European Union (EU) on Tuesday described Russia's abrupt stoppage of gas supplies to the bloc via Ukraine as "completely unacceptable".?

"Without prior warning and in clear contradiction with the reassurances given by the highest Russian and Ukrainian authorities to the EU, gas supplies to some member states have been substantially cut. This is completely unacceptable," the EU's Czech presidency said in a joint statement with the European Commission.

In the strongly worded statement, the EU demanded that gas supplies be immediately restored and Russia and Ukraine resume negotiations immediately with a view to a definitive settlement of their commercial dispute.

Russian gas giant Gazprom halted supply of natural gas to Ukraine on Thursday after the two sides failed to reach a deal on a contractual dispute.

Six European countries including EU member states such as Bulgaria, Greece and Romania reported a complete shut-off of Russian gas transmitted via Ukraine on Tuesday, signaling a dramatic escalation of the gas row.

Both sides have blamed each other for the abrupt drop in supplies.

Russia said earlier it would cut gas flow through Ukraine by 20 percent as Kiev was siphoning off the same amount of gas intended for the EU, while Ukraine said it was necessary to maintain pressure in the pipelines.

Gazprom said Tuesday's abrupt cut-off had come because Ukraine had shut three out of four transit gas pipelines, a claim denied by Ukraine's gas company Naftogaz.

The EU had said Monday there was no immediate danger to gas supplies to the 27-nation group although there were some minor disruptions, but the latest development would be more worrisome.

In its statement, the EU said it intends to continue talks with both Russia and Ukraine in efforts for the two sides to reach an immediate agreement.

(Xinhua News Agency January 7, 2009)