MOSCOW (Reuters) - Russia said on Monday it had summoned Greece’s ambassador to Moscow and told him it was responding in kind to what it called an unfriendly decision by Athens to expel two Russian diplomats.

Greece said in July it had expelled two Russian diplomats and barred two other people from entering the country for trying to bribe officials and foment demonstrations to thwart a deal to allow Macedonia to join NATO.

Russia flatly denied the allegations.

The Macedonia issue is sensitive in Greece, where political stability is pivotal as the country emerges from a huge debt crisis. Prime Minister Alexis Tsipras’ fragile left-right coalition recently lost two lawmakers who quit after a deal between Athens and Skopje to rename Macedonia, bringing his parliamentary majority to 152 out of a total of 300 seats.

Greece’s decision to expel the Russian diplomats plunged relations between Moscow and Athens, which have religious and cultural links spanning centuries, into a rare crisis.

The Russian Foreign Ministry said on Monday it had hit back, summoning Greek Ambassador to Moscow Andreas Friganas and handing him a note informing him “of tit-for-tat measures taken by the Russian side.”

The ministry, in its statement, did not name the Greek diplomats it had expelled or say when it had asked them to leave.

However, Russia’s state-backed RIA news agency cited an unnamed source as saying Moscow had expelled Greece’s trade representative as well as a Greek diplomatic employee responsible for the country’s communications policy in Russia.

A senior official from Greece’s Foreign Ministry had also been banned from entering Russia, RIA cited the same source as saying.

Russia’s ambassador to Greece called the original allegations against Russian diplomats “nonsense” and accused Athens of acting without evidence, while the Russian Foreign Ministry warned of unspecified consequences.

That prompted its Greek counterpart to tell Moscow to stop interfering in the domestic affairs of a foreign country.

Following the initial diplomatic expulsions, Greece said it still sought good relations with Russia.

However, ties have only deteriorated since, and Russia’s ambassador to Athens was reported as saying last month that the timing of a planned visit to Greece by Russian Foreign Minister Sergei Lavrov in September was no longer suitable.