The EU has warned Russia and Belarus not to allow a growing "gas war" to affect Europe, as Lithuania became the first country to complain its supplies had been hit.
By Andrew Osborn in Moscow
Energy commissioner Guenther Oettinger said other nations should not fall victim to the dispute over unpaid bills.
It came as Lithuania, a country that is totally dependant on the Russian gas it receives via Belarus, appeared to be the first country to be hit. It said it was getting 30 per cent less Russian gas than usual from the pipeline.
Earlier this week, Belarus, traditionally a Russian ally, threatened to start siphoning off gas bound for other European countries to keep its own economy going.
Mr Oettinger said: "Europe must not be taken hostage in this dispute. This is an issue between Belarus and Russia."
Russia, the world's largest energy exporter, supplies Europe with a quarter of its gas with one fifth going via Belarus.
Russia and Belarus have fallen out over a ?130 million unpaid bill and Moscow has begun cutting supplies in an attempt to get it to pay up.
It cut 15 per cent on Monday, raised that to 30 per cent on Tuesday, and then increased it to 60 per cent yesterday with a threat it would soon reduce supplies by a crippling 85 per cent.
Dalia Grybauskaite, Lithuania's president, said the situation was a reminder that the EU needed to guarantee the security of its member states' energy supply.
"The repeated form of dealing with relations, especially in the field of energy, between Russia and other countries should raise concerns for the whole of Europe," she said.
Belarus believes Russia is using the dispute to punish it for trying to develop relations with the EU and the US, while Russian analysts believe Alexander Lukashenko, Belarus' neo-Soviet president, is playing politics ahead of a crunch election next year.