A Greek envoy in Moscow was summoned by the Russian Foreign Ministry over the expulsion of the two Russian diplomats and a travel ban on two more earlier this summer.
As Sputniknews reports:

“On August 6, Greek Extraordinary and Plenipotentiary Ambassador in Russia Andreas Fryganas was summoned to the Russian Foreign Ministry where he was presented with a note informing [Greece] of the retaliatory measures taken by the Russian side in response to Athens’ unfriendly actions toward Russian diplomats and nationals in July this year,” the ministry said in a statement.

Moscow’s reaction was triggered by the expulsion of Russian diplomats in July. According to Athens, they intended to thwart a deal between the Former Yugoslav Republic of Macedonia (FYROM) and Greece, which would allow FYROM to join NATO.
Athens expelled two Russian diplomats and imposed a travel ban on two more, accusing them of meddling in security issues and attempting to bribe Greek officials.
Addressing the row, Moscow deemed the expulsion to be a “provocation” and pledged to respond reciprocally to Greece’s move.