Stockholm - At least nine people, including eight Romanian nationals, were arrested Tuesday on suspicion of pimping or sex trafficking, police said.
Police raided several locations in Stockholm and southern Sweden early Tuesday after a period of surveillance.
The probe was triggered after anti-vice police spotted a group of young women in mid-August on a street in downtown Stockholm often frequented by prostitutes.
The suspects were suspected of having smuggled a dozen women from Romania to Sweden, some believed to be aged 18 or less.
After questioning the women were released and offered to leave the country or be taken into care by the authorities, police officer Greger Casselborg told Swedish radio.
Some media reports suggested that police had also identified some 10 men who had violated a 1999 law, which makes it a criminal offence to purchase sexual favours. Swedish law does not punish the prostitute who offers these services.
Migration and Asylum Policy Minister Tobias Billstrom on Monday floated an idea that women who were victims of trafficking could be offered asylum if they were willing to testify against the traffickers.