The network profited not only from sexual exploitation, but also from selling stimulants and drugs to clients.

"The victims were kept in conditions of slavery; they had to be available at all times," the national police said.

Some of the women were already on the Spanish mainland or "had travelled from China to Spain after accepting purported job offers as therapeutic massage therapists, with a salary of around 2,000 euros a month, or as cooks or caregivers," the statement said.

The operation ended with 14 arrests: 12 in the Balearic Islands and two in Barcelona.

Seven of those arrested were remanded in custody.

All the detainees are Chinese nationals except one, a Spaniard.

"Money was sent to Chinese citizens in charge of converting it into yuan, after which it was deposited into bank accounts in China," the police said.

The women were forced to work "24 hours a day, seven days a week, without freedom of movement and with no possibility of refusing any client".

The police received two anonymous reports, and one of the victims managed to escape and reported having suffered sexual and physical assaults, a testimony that was "crucial" to the investigation.