Officers in France announced on Wednesday that they had made over 30 arrests in both France and Romania, after a near three-year investigation.

The pimping operation saw young women recruited in Romania and then taken over to France where they would tour numerous cities, serving clients as they went.

They were dubbed “sex tours” because the women were constantly moved around French cities for a short period of time, before going back to Romania. The tactic made it harder for police to track them down.

In teams of six they would often work out of hotels or apartments rented in the short term in cities such as Paris, Lyon, Marseille, Dijon and Bordeaux.

According to investigators the women would serve up to as many as 15 clients a day often under threat or violence.

The organised “sex tours” are seen as a relatively new form of prostitution.

Police in France were made aware of the nature of one operation when they busted a prostitution ring in Paris and realised the women had recently stayed in the cities of Rennes, Rouen and Nantes.

Investigators said each woman would normally bring in around €8,000 a month, which would be invested in property and nightclubs back in Romania.

investigators believed the pimps behind the network earned as much as €4 million in two years. 

The three people arrested in France were picked up by police in Marseille, Aix-en-Provence and Bordeaux.