Ukrainian authorities claim to have busted a Hungarian spy ring operating on its territory, alleging that Budapest was collecting sensitive military data with one eye on a possible future incursion into the west of the country.

Hungary’s foreign minister dismissed the accusations as “propaganda” and announced the expulsion of two Ukrainians described as “spies working under diplomatic cover” at the Ukrainian embassy in Budapest.

The allegations will further test already fraught relations between the two neighbouring countries. While Hungary is a member of Nato and the EU, its prime minister, Viktor Orbán, has been an outlier among European leaders, strongly critical of Kyiv and neutral towards Russia.