The embassy tweet came after more than 50 Ukrainian prisoners of war (POWs) held by Russia were killed - Azov soldiers reportedly among them.
They died in an attack on Olenivka prison in Russian-held eastern Ukraine.
Ukraine and Russia blame each other for Friday's attack in the Donetsk region.
Twitter acknowledged that the post from the Russian embassy violated the social media company's "rules about hateful conduct" - but added that it may be in the public interest to keep it accessible.
