The bodies of the two Chinese women were discovered in a residential building in the upmarket Prati district on Thursday morning, while the body of the South American was found in an apartment in the same neighbourhood an hour later.
All three victims were stabbed, according to Italian media reports.
According to the Corriere della Sera newspaper, footage from surveillance cameras allowed police to identify 51-year-old Giandavide De Pau, who had been prosecuted in the past for drug trafficking and sexual assault.
The suspect is reportedly a member of a mafia clan headed by Michele Senese, who is currently serving a life sentence. De Pau is believed to have been one of Senese’s closest collaborators, acting as his personal driver and handyman.
In 2008 and 2011, the suspect had also spent time in a psychiatric hospital.
It is unknown whether the suspected killer was carrying out a mafia hit or acting alone, possibly under the influence of drugs, which were found at the home of some family members where he is believed to have sought refuge after the police manhunt got underway, Corriere della Sera reported.
Several newspapers had warned of a possible “serial killer” in the Italian capital.
The body of one of the Chinese victims was spotted by a neighbour where it lay, naked on a landing. The woman, believed to be in her 40s, had suffered head and stomach injuries, the newspaper said.
When police entered her apartment, they found the body of the second Chinese woman.
Nobody in the building appeared to have heard the murders take place, according to residents.
“Everybody knew there was a house of ill repute here, I’d see people arriving at 2:00 am, 3:00 am,” a woman who lived in the building told reporters.
The body of the Colombian, who was 65, was found by a friend, Corriere della Sera said.