Police in the southern Indian state of Kerala have arrested the mother and stepfather of a teenage girl for allegedly forcing her into the sex trade for two years.

The 13-year-old has been rescued and taken to a state-run shelter home.

She has told counsellors that her parents would solicit customers and force her to have sex with the men.

Her mother has told a news channel that she would charge 3,000 rupees (£30; $47) from a customer for her daughter.

Police said they had identified 25 of the 40 customers who had allegedly paid for sex with the teenager.

Ten others, including a broker, have also been arrested in connection with the case.

The 37-year-old mother has seven children - the oldest is 24 years old and the youngest is aged four.

Her 55-year-old husband worked as a driver and would solicit customers showing the girl's photograph, police said.

The family lived in a rented house in the town of Kottakal in Malappuram district in the north of the state.

In 2011, police in Kerala arrested the father of a 17-year-old girl for forcing her to have sex for money with up to 200 men.

Twenty-nine others were arrested in connection with the case.