Ukraine says it has expelled two Hungarian diplomats hours after the country’s main security agency said that it had arrested two people on suspicion of spying for Hungary by gathering intelligence on Ukraine’s military in the west of the country.

Ukrainian security services claimed to have uncovered a Hungarian spy ring gathering information about military activities in Ukraine’s western Transcarpathia region.

Tensions exist between Ukraine and Hungary, whose leader Viktor Orbán is sympathetic to Russia and skeptical of Western intervention in the Ukraine war.