A task force of female officers from West Midlands Police were sent to a massage parlour in Birmingham to free the women on Thursday.
Two people, believed to be customers, were detained during the operation, and one sawn-off shotgun recovered. Three people - a 40-year-old woman from Brierley Hill and two men who were believed to be managers - were arrested.
A force spokesman said: "The women are believed to be of eastern European origin and were tricked into the sex industry.
"They had their passports taken. They were locked into the venue during the evening to work and taken away during the day and locked in a house."
The raids took place at Cuddles massage parlour in Birmingham at 7pm.
Amnesty International welcomed the raid but called on the British Government to do more to protect victims of trafficking.
The human rights group said the Sexual Offences Act and the Asylum and Immigration Act, which both came into force last year, were helping police to catch and prosecute traffickers, but urged ministers to do more. The Amnesty spokeswoman Sarah Green said there was no protection in law for victims of trafficking, who were classed as illegal immigrants and deported.
She said: "Most are deported without any care or support or assessment of the risks they face if sent back.
"Communities might not want these women back if they know what has happened to them, and there is evidence of people being re-trafficked.
"If you deport them very quickly and arbitrarily, you are simply throwing them back into the fire."
Ms Green appealed to the Government to sign up to the Council of Europe Convention on Action against Trafficking in Human Beings, which she said gave victims the right to emergency housing and medical care and a temporary residence permit in the country they found themselves in.
"There's no reason why Britain should not sign up," she said.
"These people are victims of a series of vicious human rights violations and should be protected in law."
Ms Green said Britain had a responsibility to protect such women who were brought to the country because of demand.
Fifteen nations have already adopted the convention, including Italy, Portugal and Austria.Reuse content