Hungarian Foreign Minister Peter Szijjarto told a meeting in Vienna of the International Atomic Energy Agency (IAEA) that "some entities in the European Union are...continuously making attempts to put hurdles and obstacles in (the) way of nuclear investments."

"I want to make it very clear here that we do consider all actions carried out... to put obstacles on the way of the construction of our nuclear power plants as attacks against our sovereignty."

The landlocked central European country is exempted from the partial EU embargo on Russian oil and rejects calls for other sanctions on Russia's energy industry, even indirect ones on areas such as construction, engineering or IT.

Sanctions on nuclear investments were a "red line" for Hungary and would be "a violation of European regulations", Szijjarto told the United Nations nuclear watchdog.

"We would never support... any sanctions that would endanger our safe energy supply," he said.

Hungary's nationalist prime minister, Viktor Orban, has sought close ties with Russian President Vladimir Putin in recent years and has frequently railed against EU sanctions against the Kremlin, arguing that they hurt Europe more than Moscow.

Hungary is due shortly to start construction of two new nuclear reactors with Russian conglomerate Rosatom.

They will supplement Hungary's four existing atomic reactors, which run on Russian fuel and supply around half the country's electricity.

EU member states in favour of strong sanctions against Russia are pushing for an end to nuclear cooperation with Moscow. They include the Baltic states, Ireland and Poland.

But there is no consensus on the issue among the bloc's 27 members, a European diplomatic source told AFP.

Bulgaria, which lost access to Russian gas supplies because the previous centrist government refused to pay in rubles, is also concerned about talk on widening the energy embargo.

Its one and only nuclear plant supplies about a third of the country's power.

On Monday, Orban again criticised the EU's strategy.

"Europe is shooting itself in the foot," he told parliament in Budapest.

"A dwarf is imposing sanctions on a giant when sanctions can only work if it's the other way round."