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.

Ukraine and Hungary said on Friday they were expelling two diplomats each after each side accused the other of engaging in espionage.