A 29-year-old Indian woman who was sold into sexual slavery as a teenager has written to Prime Minister Narendra Modi, urging him to rescue hundreds of thousands of other girls who are trapped in brothels and raped daily. In a two-page letter written in Hindi, the woman – who identifies herself as Tavi - described how she was duped and trafficked to a brothel in Mumbai when she was 17, and sold for sex for six years before police rescued her. The letter has made headlines in India, a country with the world's highest number of enslaved people but which has only recently stepped up efforts to tackle modern slavery. "I got help and I was rescued. There were many girls like me there. I didn't see any of them escape or leave. I have written the letter for girls like them," Tavi told the Thomson Reuters Foundation in an interview on Thursday. "These girls are unemployed - they have no work, no money. People lure them to Mumbai, promising them work. The PM should also ensure there are job opportunities for girls so that they don't fall in this trap." Almost 46 million people are enslaved worldwide – trafficked into brothels, forced into manual labor, victims of debt bondage or born into servitude, says the 2016 Global Slavery Index. Forty percent, or more than 18 million, are in India. Many come from poor rural regions and are lured with the promise of good jobs or marriage but end up sold into domestic work, or toiling in brick kilns, textile units or prostitution. The number of women sold into sexual slavery is unclear, but studies estimate there could up to 20 million Indians – almost half below the age of 18 - working in the sex trade alone. In her letter to Modi, Tavi described how she was lured from her home in the eastern city of Kolkata in 2005 by her then boyfriend, who promised to marry her once they eloped to Mumbai. Instead, he sold her for 60,000 rupees ($935) to a brothel. For six years, she was moved to various brothels in the area. She was finally rescued during a police raid in 2011. The letter was given to Modi on Monday to mark the Hindu festival of Raksha Bandhan, which celebrates the bond between a brother and sister. Tavi, who now works in a garment factory in Mumbai, said Modi was like a brother to her and the other women and girls trapped in sex work, and that it was his duty to protect them. "I was a victim of human trafficking and my life was hell. I was beaten and abused and treated worse than an animal. I used to think that I would die in the brothel," she wrote. "Even now there are many women trapped in brothels. You are a brother to all these women. I request you to protect them." A government official who delivered the letter to Modi said he had promised to reply.