Hate graffiti and far-right symbols were found on a cinema, an LGBT centre, the university, a cemetery and the offices of left-wing candidates in March's council elections.
The inscriptions attack Jewish groups and freemasons and assimilate Jewish people with homosexuals.
The city's Socialist mayor, Pierre Cohen, said he was "deeply shocked" by the attacks.
"Those hateful messages are a real danger for our republic," he said in a statement. "It is our responsibility not to let this noxious atmosphere reminiscent of the inglorious past become established."
About 20 supporters of the controversial comedian Dieudonné, previously convicted for anti-Semitic insults, gathered in the city's main square on Sunday for a "quenelle party", according to police.
The quenelle, a gesture popularised by Dieudonné, looks like a reverse Nazi salute according to his detractors, although his supporters insist it is just "anti-system".
Islamist Mohamed Merah murdered three children and one teacher at a Jewish school in Toulouse after killing three soldiers elsewhere in 2012.
On Friday the far-right Front National dropped one of its local council candidates in Chateauroux, central France, after pictures showing of him with Nazi-themed tattoos were published on the internet.