Slovak refinery Slovnaft on Wednesday said Russian oil was once more flowing to the EU member through Ukraine after supplies had been halted due to sanctions.
"Crude oil is already arriving again in Slovakia through the Druzhba pipeline, and in Hungary the supply is expected to be restored tomorrow," spokesman Anton Molnar told AFP.
Russian firm Transneft on Tuesday said that deliveries to the Czech Republic, Hungary and Slovakia through Ukraine had been halted last week.
The company said the Ukrainian side stopped the oil transport "due to not receiving funds for these services".
Molnar had said on Tuesday that "there were technical problems at the bank level in connection with the payment of transit fees from the Russian side".
Since President Vladimir Putin sent troops to Ukraine, Washington and Brussels have pummelled Moscow with unprecedented sanctions, cutting Russia off from international financial institutions.
Molnar said on Wednesday that Slovnaft and its Hungarian parent company MOL had volunteered to pay the transit fees to resolve the issue.
He said both the Ukrainian and Russian sides had agreed to the idea.
Supplies to the Czech Republic have still not resumed, according to Barbora Putzova, spokeswoman for the Mero company that runs the Czech part of Druzhba.
"The most important thing for us as the transit company is that there is no technological issue and that we have enough oil," she told AFP.