Slovakia has rejected a call by the EU to scrap a measure that introduced different pricing for foreign and domestic vehicles at petrol stations, Prime Minister Robert Fico said on Monday.

The government in Bratislava introduced a 30-day restriction on diesel and fuel on March 18 as oil prices had begun soaring due to the war in Iran.

In a bid to prevent drivers from neighbouring EU countries stocking up on cheaper fuel in Slovakia, the country also increased prices for vehicles with a foreign licence plate, arguing that supplies could currently only be maintained thanks to state emergency reserves.

A spokesman for the European Commission recently described the measure as "highly discriminatory," and Fico said the commission had threatened his government with infringement proceedings over alleged violations of EU law.

However, Fico rejected the request to withdraw the different pricing as "utterly unfair to Slovakia" and did not rule out extending the measure.

Instead, he called on the commission to put more pressure on Ukraine to ensure that it resumes the transit of Russian oil to Slovakia, which he said would make all restrictions unnecessary.

Slovakia issued an "oil emergency" shortly before the Iran war began on February 28, after oil stopped flowing through the Druzhba pipeline from Ukraine in mid-January.

The Druzhba pipeline delivered Russian oil through Ukraine to Hungary and Slovakia. According to Kiev, the pipeline was damaged by Russian drone strikes, causing the halt to deliveries.

Slovakia and Hungary have questioned Ukraine's account and called for an independent inspection of the pipeline.

Slovakia remains highly dependent on Russian oil deliveries and has been granted an exemption from EU sanctions against Russia to be able to import Russian oil and cope with the shortage.