A Thessaloniki prosecutor on Monday ordered a preliminary investigation into far-left activists' claims to have carried out an "anti-Zionist patrol" in the northern port city to protest Israeli investments in Greece.

The investigation will look into whether the Rubicon group can be held liable for incitement to committing crimes of violence or hatred, and threatening to commit crimes.

The probe followed a social media posting by the group, showing pictures of men dressing in uniform black outfits blazoned with a Palestinian flag apparently marching through central Thessaloniki on Saturday.

Thessaloniki's once-thriving Jewish community was rounded up by German occupation troops in World War II and sent to Nazi death camps in Poland and elsewhere, where the majority was murdered.

The post said the group staged the "patrol" in a part of the city "where Israeli capital has parasitically intruded." It added that Israeli and other funds "are massively buying up beaches, neighborhoods and villages, turning their residents into migrants in their own land."