The Greek Kathimerini daily earlier reported citing diplomatic sources that Athens had chose to expel two Russian diplomats and ban two others from entering the country.
"Our assessment is that such behavior took place, and all [necessary] measures will be taken", Tzanakopoulos said without providing any additional information.
They also point to the careful stance Greece took in the Skripal affair when it did not follow other Western countries that expelled Russian diplomats, a position that was welcomed by Moscow.
However, the impression given by both Tzanakopoulos and diplomatic sources was that Greece had taken issue with the Russian envoys in question, not the entire Russian mission to Greece. The Greek government will not tolerate disrespect for global law and the Greek state, Greek Cabinet Spokesman Dimitris Tzanakopoulos said on Wednesday commenting on reports concerning the Greek authorities' decision to expel two Russian diplomats and ban two others from entering the country.
Greek sources indicated that such a move would be unjustifiable and would lead to a further deterioration of ties.
Diplomats in Athens on Wednesday elaborated on the insights revealed by Kathimerini's report, noting that Greek authorities had long warned Moscow about the behavior of the Russian diplomats.
According to the sources, the diplomats are accused of interference in home affairs, attempted collection and dissemination of information, and bribery of government officials.
According to one of the sources, any response from Moscow would only aggravate the situation.
Greek newspaper Kathimerini is reporting on its website that two more Russian diplomats have been banned from entering the country.
Last month Macedonia and Greece agreed to end a 27-year row by renaming the ex-Yugoslav state the Republic of North Macedonia.