Russia and Ukraine have invited the European Union to see for itself which country is to blame for the cut in supplies that has prompted Slovakia to declare a state of emergency and Bulgaria a crisis.
Ukraine wants EU monitors to confirm that Russia's energy company Gazprom is sending no gas down the pipeline.
Moscow says it has been, but is now cutting supplies.
It says Ukraine was stealing gas meant for other European countries.
Much of Europe gets its gas from Russia through Ukraine and they are being affected by the dispute.
Bulgaria, the Baltics, Slovakia and Hungary are almost 100% dependent on Russia for gas and some places have had no gas for more than 24 hours.
Romania, Bosnia-Hercegovina, Croatia, Greece, Macedonia, Serbia, and Austria have also had their supplies reduced.
The BBC's business reporter Louise Cooper described the situation.
Listen Listen to Louise Cooper (3 mins 16 secs)
The BBC's correspondent in the Ukranian capital, Kiev, is Gabriel Gatehouse.
Is there much urgency within the government to sort this out?
Listen Listen to Gabriel Gatehouse (1 min 13 secs)
Iva Vukusic lives in the Bosnian capital, Sarajevo. She described how cold it is there.
Listen Listen to Iva Vuvsic (2 mins 51 secs)
First broadcast 7 January 2009
To see a map of the affected area, click here.
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