Russia's decision to sever oil supplies to Europe was "unacceptable", German Chancellor Angela Merkel has said, according to BBC.
European Commission President Jose Manuel Barroso had said earlier that energy companies should not be allowed to cut off oil supplies unannounced.
Their comments came as a high-level delegation from Belarus arrived in Moscow for talks with Russia aimed at resolving a dispute over oil supplies.
Russia halted oil exports to Belarus on Monday, accusing Minsk of stealing oil.
'Alternative supplies'
Ms Merkel added that cutting supplies without consultation "destroyed trust".
The European Commission is convening its oil supply group on Thursday to discuss the impact of the cuts, amid reports that some refiners are now being affected.
In a statement, it warned that the current situation made clear the need for Europe to reduce its dependence on imported oil and gas - a focus of its energy review, due to be unveiled on Wednesday.
European legislation requires member states to hold emergency stocks, which the commission said stood at more than 120 days. The International Energy Agency (IEA), a multilateral energy think-tank, has said that this means European oil markets should be able to cope with the shutdown.
It added that even if the shut-off was a prolonged one, refineries "could source crude supplies from alternative routes, and some of them are already organising alternative supplies".
Azerbaijan also is in dispute with Russia and has suspended oil exports to Russia following a pricing dispute with state-backed gas giant Gazprom.
'No threat'
Belarus has been rowing with Russia over charges relating to oil and gas. Russia has been pushing prices higher, and also started to charge duties on its crude oil shipments - which had previously been duty-free, on the understanding that profits from refined oil should have been shared.
Russia's moves prompted Belarus to impose a transit tax on the Russian oil being shipped through pipelines that transited its territories.
It then launched a legal action against Transneft when the Russian oil pipeline monopoly refused to pay the charges.
Belarus has said it is ready to negotiate over its decision to introduce a $45 (£23) per tonne charge for oil shipped through its territory.
The wrangle prompted Russia to shut off the transcontinental pipeline through Belarus, halting the flow of oil to Germany, Poland and beyond.
German Chancellor Angela Merkel - whose country currently holds the presidency of the EU - is meeting the EU Energy Commissioner in Berlin.
Ms Merkel told German TV the row showed the need to diversify energy sources.
Escalating rows
The latest energy wrangle comes almost a year after deliveries of Russian natural gas to much of Western Europe were disrupted during a dispute over pricing between Russia and Ukraine.
However the current row between Moscow and Minsk is resolved, Natalia Leschenko, an analyst at Global Insight, said she expected it to end soon - and at the expense of Russia.
"Transneft and the Russian government are looking to face financial losses and damaged reputation, whereas the outcast status of Belarus in Europe gives it the benefit of invulnerability, which its government uses in full," she said.
(BBC News, 09/01/2007)