Attackers on a motorcycle threw a hand grenade at the Russian consulate in Athens early on Friday, causing no injuries and slight damage, police said.
There was no immediate claim of responsibility for the early morning attack on the consulate in the Athens suburb of Chalandri. Police had cordoned off the area.
The device exploded beneath a guard booth in the compound of the consulate but was thought to be low-density explosive.
"The material damage was small and there were no injuries," a police spokesman told Reuters.
Greece's Ministry of Foreign Affairs said it "unreservedly condemned" the attack.
"Our traditional and centuries-old ties of friendship and cooperation with Russia are not going to be affected by such unlawful and utterly condemnable acts," it said in a statement.
Small-scale attacks on businesses, police, politicians and embassies are frequent in Greece, which has a long history of political violence.
A burnt-out motorcycle found shortly after the incident in the central Athens district of Exarchia was being examined as the possible getaway vehicle of the attackers.
In 2016, a security guard was wounded in a similar incident at the French embassy in central Athens.
"It would be very early to share further evidence. The anti-terrorism unit is now handling the case. We had similar attacks in the past, one particular attack was very similar," the official said, referring to the attack on the French embassy.