The investigation peaked two days ago with eight house searches and the arrest of a 52-year-old woman and a 48-year-old man, Criminal Police head France Božičnik said at a news conference in Novo Mesto on Friday.
The woman was involved in organising prostitution for at least 14 years with several women, he explained.
Božičnik mentioned one Ukrainian and two Serbian women who had had at least 1,600 "sex contacts" during this period, or even 20 per day per prostitute.
Their services ranged from 40 to 100 euro, meaning the two suspects had gained at least 95,000 euro during this period.
The police charged the suspects with 12 counts of crime, and the investigating judge remanded them in custody.
If found guilty, they could get from one to 12 years in prison.
The police said the suspects "acted extremely carefully and cunningly", recruiting unemployed women from socially underprivileged backgrounds.
The women were forced to work in various flats and hotels all day long. They were stripped of half of their earnings and made to pay for the rented rooms and flats and for transport.
While they fully controlled them, the suspects did not take care of their health, social or labour security, Božičnik explained.
He also said that the suspects had lived a lavish lifestyle although they were jobless.
The Novo Mesto Crime Police boss also said the investigation, which was launched in mid-March, was "extremely demanding".
Although they got first information about the criminal activity in April 2017, it took almost a year to obtain enough evidence to launch a proper investigation.
The investigation had been carried out in collaboration with the Celje and Maribor Police Departments.
Meanwhile, Celje police said in a press release it had arrested six persons after searching several houses on suspicion of human trafficking and prostitution, but added that more information would be provided at a news conference on Monday.
