Johannes Steiner, an activist from Graz, shared a picture of the van, which he had been sent by a female resident, and filed charges, according to the local Kleine Zeitung.
The local newspaper said that when Steiner filed charges, he discovered that the van had already been reported on June 24th, so it had apparently already been on the road for at least a few days.
Beneath the slogan was the URL of a website, blurred out in the photo but which reportedly contained "conspiracy theories" and attacks on the Austrian justice system and police. It is not apparent if the van's driver or owner is responsible for its content.
Austria has several laws in place against hate speech, Holocaust denial or use of Nazi symbols.
In February, a 23-year-old was fined and given a conditional sentence of one year after making anti-Semitic Facebook posts which praised Hitler.
Personalized car number plates with abbreviations or number combinations linked to the Nazi movement are banned, such as HJ (Hitler Jugend) or 88 (which stands for Heil Hitler).