More than 130 premises have been raided and eight people arrested in a cross-border operation targeting organised prostitution, criminality and money-laundering.
The operation in the south involved more than 200 officers and was led by members of the Organised Crime Unit based at the National Bureau of Criminal Investigation supported by officers from all Garda regions.
A man in his 40s and a woman in her 20s are being questioned at Dundrum garda station, and a woman in her 20s is being held in Store Street garda station.
Police in the North rescued three suspected victims of human trafficking when they searched 10 brothels yesterday.
Five people were arrested as every county across the north, and Belfast and Derry cities, were visited during Operation Quest.
At the same time detectives in the south searched 114 apartments, flats and houses. One man and two women were arrested for questioning.
A significant amount of documents, cash, mobile phones and computers were seized in both jurisdictions and are expected to result in several bank accounts being frozen.
PSNI Detective Superintendent Philip Marshall said: “We are determined to actually do something about this problem. It is not something society should stand for. It is a criminal offence and police do take it seriously.”
He said yesterday’s events demonstrated the commitment of the Gardaí, PSNI and other law enforcement agencies across Europe.
Officers in the North visited more than 20 addresses and searched several of them.
A PSNI spokesman said they believed 10 of these locations were being used for the purposes of prostitution. The operation resulted in five arrests for a variety of offences and three suspected victims of human trafficking were rescued, police added.
It involved 170 police officers across the North and had been planned for several weeks.
Detectives received support from women’s help organisations who deal with rescued victims of trafficking and representatives of the Gardaí were in the Belfast command room. Women were taken to special suites at police stations for dealing with those trapped in the sex trade.
Police questioned one woman discovered at a flat in the city centre. A team of officers with specialist equipment including heavy duty lock breakers had mustered nearby and broke into the locked flat within seconds after a knock to the door went unanswered.
Three or four officers pushed the door open, rushed into the room shouting “police” and found the woman, of foreign appearance, inside. Police wearing rubber purple gloves conducted a thorough search and gathered evidence in a special plastic bag.
The woman was later led away for questioning, a black coat hiding her features from cameras.
Det Supt Marshall said officers were responding to concerns in wider society about sexual exploitation and human trafficking.
“Today’s operation is focused on getting information and evidence on the extent of the problem of organised prostitution in Ireland,” he added. “We suspect there is a number of crime gangs involved in this.”
The probe was not focused particularly on paramilitaries.
A garda spokesman said: “During the investigation to date it has been established that prostitution is organised on a cross-border basis and today’s joint operation was specifically aimed at individuals and groups intent on making profits from vulnerable members of society across the island of Ireland.
“The policy of An Garda Siochana is to treat women involved as witnesses/victims unless significant evidence comes to light suggesting direct involvement in organised prostitution or brothel-keeping.
“Specific training has been provided to gardaí investigating this type of crime who continue to liaise closely with various support groups working in this area.”
Gerardine Rowley, of support group Ruhama, said the cross-border operation across the island of Ireland was a new approach to helping victims of prostitution, who would be treated as witnesses.
Almost 60 alleged victims of human trafficking – including six Irish children - were reported to gardaí last year.
“Organised prostitution has been growing the last number of years and criminals don’t see a border,” she said.
“This is going after the organisers who are making money from women who are vulnerable and controlled.”
An organisation that campaigns for ethnic minorities has said the North had the fastest growing sex industry in any part of the UK.
The claim was made as Stormont Justice Minister David Ford announced plans for two new laws to combat human trafficking. Between April last year and February this year police identified 26 potential victims in the North from countries including Ghana, Zimbabwe, China and Slovakia.
In February, a man was convicted for trafficking in a court in the North for the first time.