Florence police Chief Raffaele Micillo told Sky TG24 TV that 55-year-old plumber Riccardo Viti confessed on Friday to the slaying.
He said Viti's DNA is being compared to samples from similar cases. Among 10 other cases involving area prostitutes was one last year of a woman found - alive - tied to a metal gate in a similar fashion.
Earlier in the week, a passer-by spotted the body of the 26-year-old Romanian woman tied to bars under a highway overpass near the town of Scandicci.
Police say several prostitutes who had escaped a client who tortured them provided valuable clues.