New Delhi, March 13 -- Hungary's government will declassify a national security report that the populist prime minister says will prove his main political challenger received illegal financing from Ukraine, a minister said Thursday.

Prime Minister Viktor Orban faces the biggest political challenge of his career in next month's elections, where he is trailing in most polls behind his center-right opponent, Peter Magyar and his Tisza party.

As the April 12 vote approaches, Orban - who maintains cordial relations with the Kremlin - has relied increasingly on an aggressive anti-Ukraine campaign that alleges Kyiv, the European Union and Tisza are part of a conspiracy to oust his government and install one that makes decisions more favorable ...