Moscow has reportedly threatened to retaliate to Athens' intention to expel two Russian diplomats stationed in Greece.
According to the Russian news agency Interfax, the Russian foreign ministry announced that a response is expected "in the same manner" by Moscow.
An earlier report by the Athens daily "Kathimerini" said Greece has already decided to expel the two diplomats, who are suspected of trying to collect confidential information over a recent bilateral agreement to resolve the fYRoM "name issue", and even attempts to bribe state officials.
According to the press report, the government in Athens believes the pair tried to intervene in negotiations.
Another two Russian diplomats were reportedly blocked from entering the country.
Diplomatic sources quoted by the newspaper claimed that Greek counter-intelligence has recently focused on attempts - ostensibly by Moscow - to acquire more influence in municipalities, ecclesiastical jurisdictions and even Mount Athos.
The same sources pointed to an "effort to intervene in Balkan issues affecting the country (Greece), and especially the fYRoM 'name issue'."
Asked about the press report, a government spokesman in Athens later appeared on an Athens-based broadcaster, where he essentially confirmed the incident.
"... everyone must respect international law... the Greek government and the Greek state ... within this framework, whenever necessary, we will take measures, something that has been done in this case... we cannot accept behavior that violates Greek law," spokesman Dimitris Tzanakopoulos said.