Under a 15-year contract signed on Monday, Hungary will take delivery from Gazprom of an annual 4.5 billion cubic meters of gas, of which 3.5 bln will come through an interconnector with Serbia and 1 bln from a pipeline from Austria. Hungary's gas imports from Russia have been delivered through Ukraine until now.

In his post on Facebook, Szijjártó said parties with whom Hungary decides to reach agreements and the content of those agreements is "none of the Ukrainians' business".

"We consider it a serious violation of our sovereignty and national security interests that [the Ukrainian government] wants to obstruct Hungary's secure supply of gas, the heating of Hungarians' homes and the operation of the country's industry," he said.

The minister added that the Ukrainian measure was "unfriendly" considering support the country has received from Hungary, such as "ventilators, healthcare equipment, the care of soldiers, holidays for children and the financing of investments".

He added that Ukraine's ambassador to Hungary has been summoned to the Ministry of Foreign Affairs over the matter.