The spokesperson for Prime Minister Viktor Orban has denounced the reports by Ukrainian media.
Hungary has denied media reports that it had been warned by Russia about the planned invasion of Ukraine.
Local Ukrainian media had shared claims by a senior official in Kyiv that Budapest had been aware of the upcoming war.
Oleksiy Danilov -- the secretary of Ukraine’s National Security Council -- also reportedly stated that Hungary had been planning to annex part of its neighbour’s territory.
But the spokesperson for Hungarian Prime Minister Viktor Orban has dismissed the allegations as "fake news".
Zoltán Kovács, Hungary's Secretary of State for Public Diplomacy and Relations, also denied that Budapest had intentions to annex Transcarpathia -- home to an estimated 140,000 ethnic Hungarians.
Kovács said on Twitter that the allegations were in retaliation to Hungary’s refusal to provide Ukraine with weapons.
"While we understand that Ukraine does not welcome our decision, spreading fake news and coming up with lies will not change our position," he added.
While Hungary has voted in favour of all current European Union sanctions on Russia, it has stood firm against planned measures on Russian energy imports.
Budapest has said it was prepared to pay for gas exports in roubles, contrary to the EU's stance.
The Hungarian embassy in Kyiv also said it was "outraged" at the claims that Budapest was warned about the war.
“We strongly reject and condemn the slander that has been made against Hungary," the embassy said on Tuesday.
"We urge Mr Danilov to withdraw his statements," it said, adding that the comments could incite hatred against the Hungarian people.