Moldova said Tuesday it has expelled a Russian diplomat after Moscow opened polling stations for its presidential election in Moldova’s pro-Russia breakaway region of Transnistria.

Moldova summoned Russia’s ambassador, Oleg Vasnetsov, to protest against the Kremlin’s decision to open six polling stations in Transnistria “contrary to the position of the Moldovan authorities,” the foreign ministry said.

It said it informed Vasnetsov that an unnamed embassy worker was a “collaborator” who was declared persona non grata and must leave the country.