Hungary says it turned to Russia for COVID-19 vaccines because the EU was too slow.
Budapest, which is part of the collective vaccine purchasing programme coordinated by Brussels, has signed a deal for two million doses of Moscow's Sputnik V jab.
The European Commission says member states can make separate deals if the vaccine makers they are buying from are not already in negotiation with the EU.
"Expectations were hyped very high and now we see that the deliveries [from the EU scheme] are much slower and they contain much less vaccine than they were supposed to do," Hungary's foreign minister, Péter Szijjártó, told Euronews.
"And still, some European institutions and bureaucrats continue to attack countries which are looking for different or alternative sources in this regard.
"It's a matter of life of the people which we have to save. And if we see that the common purchase or common procurement managed by Brussels is too slow, then we have to secure additional supply to the Hungarian people."
Szijjártó also complained that pharmaceutical companies were delivering more doses to countries outside the EU.
"The producer, which has been prioritised by the European Union very heavily, is delivering more vaccines to [the] US, UK and Israel compared to EU member states," he added. "This is a fact and I think it needs at least to be explained to a certain extent.
"And we see [the] UK using the product of AstraZeneca to vaccinate British citizens. The European Medical Agency (EMA) has not given its approval yet [for AstraZeneca], which needs an explanation as well."
Hungary hasn't started inoculating its citizens with the Russian jab. At the time of writing, the country has administered around 156,000 doses (covering 1.6% of its population) using vaccines provided under the EU's scheme.
Many Hungarians remain sceptical about Sputnik V. A Euronews poll published in November 2020 showed that only 7% of Hungarian would be willing to accept the Russian-made vaccine.
The EMA has so far approved two COVID-19 vaccines for use in the EU. The Pfizer-BioNTech one before Christmas and the Moderna jab earlier this month. It is expected to give the green light to the Oxford-AstraZeneca vaccine this week.
The EU has committed to buying 300 million AstraZeneca doses with an option on 100 million extra shots. Late last week, the company said it was planning to reduce a first contingent of 80 million to 31 million. Pfizer has said it was delaying deliveries to Europe and Canada while it upgrades its plant in Belgium to increase production capacity.