In Rev, Jesus used the phrase, "a synagogue of Satan," which means there is more than one.
"Those who say they are Jews, but are not Jews."
Sounds like crypto-jews to me. Or, those who pretend to be "men of the cloth" but are actually ravening wolves. Deceptors. In his time, the Jews were often the local governing authorities, under the Roman empire. Sounds like he is referring to what we would call, "The Cabal."
Biblical