The demonstration was held outside the embassy's Moscow headquarters on September 29 to protest Georgia's detention two days earlier of four Russian army officers on suspicion of spying. A pig's head was reportedly launched into the diplomatic mission, breaking a window.
Kakha Adali, a security guard, rushed out and kicked one of the protesters, already being apprehended by police officers, in the buttocks. Footage of the incident was shown on NTV and other major Russian television channels.
"The security guard's reaction was provoked by the aggressive and insulting behavior of the attackers," the Georgian Embassy said in a statement. It acknowledged, however, that the employee should have exercised "maximum restraint" and said he had left Russia.
Russian prosecutors have launched an official investigation into the incident.
The arrest of the Russian officers on espionage charges on September 27 triggered a wave of anti-Georgian protests in Russia and put Moscow's relations with Tbilisi under further strain. Russia recalled its ambassador from Georgia and evacuated most of the embassy personnel last week. On Monday, it also cut transportation and postal links with the South Caucasus state - a measure it did not cancel even after Tbilisi released the officers later that day.