Slovakia has declared a state of emergency in the oil sector, reports "Euroactive".
This comes 22 days after Russian oil supplies via the "Druzhba" pipeline were cut off. Soviet-era pipelines were suspended.
The state of emergency takes effect on February 19 and will last until September 30 at the latest.
The government of Prime Minister Robert Fico also said it would release 250,000 tons of strategic oil reserves at the request of the Slovak refinery "Slovnaft".
Ukrainian officials say the disruption occurred after a Russian attack on infrastructure running through Ukraine on January 27. Budapest and Bratislava remained silent for two weeks, only making the matter public after a report by "Bloomberg" and after Ukrainian Foreign Minister Andriy Szybiga announced the suspension.
Hungary and Slovakia have opposed EU efforts to gradually stop imports of Russian energy resources and have even increased their purchases since Russia began its war in Ukraine in February 2022. Both countries have objected to EU military aid to Kiev.
Over the weekend, the governments of both countries said the pipeline had been repaired but that transmission had not resumed. Hungary and Slovakia accuse Kiev of deliberately withholding supplies for "ideological reasons".
In search of alternatives, the two countries this week called on Croatia to allow Russian oil to be delivered by sea via the "Adria" pipeline. Zagreb has so far agreed to transport only non-Russian oil.
Budapest and Bratislava argue that their temporary exemption from EU sanctions entitles them to receive Russian oil by sea if supplies via the "Druzhba" pipeline are cut off.
They have sent a letter to European Commission President Ursula von der Leyen asking Brussels to protect "their legal right" to receive Russian oil by sea.
A European Commission spokesman confirmed that the institution is in contact with Kiev about the "Druzhba" pipeline, adding that it is ready to convene an extraordinary coordination group to discuss alternative fuel supply routes.
Meanwhile, "Slovnaft" - Slovakia's main refinery - has used reserves, restricted exports and secured alternative supplies of crude oil through the Adria pipeline. Its director, Gabriel Szabo, said supplies had been ordered from Saudi Arabia, Libya, Kazakhstan and Norway.
Slovak government documents show that it will take between 20 and 30 days for oil transported via the Adria pipeline to reach the country.
Hungarian Foreign Minister Péter Szijjártó assured that his country's energy supplies were not threatened.
Hungary has 90 days of oil reserves and its oil company MOL Group has already ordered a supply from Russia that could arrive in Hungary by mid-March if Croatia agrees to facilitate transit, he said.