The girl, who had gone missing near Mankhurd railway station on Sunday night, was found dead in the bushes behind RBT Colony the next day, they said.
She got separated from her mother near the railway station due to Sunday rush. Her family lodged a missing complaint at Mankhurd Police Station at around 1:30 AM on Monday after they could not find her, police said.
Police prepared a sketch of the suspect on the basis of the description provided by the girl's mother, following which Sachin Panchare (25) was arrested from his house in Mankhurd yesterday, they said.
The body has been sent for postmortem and a case was registered against the accused under relevant sections of IPC for kidnapping and murder and under Protection of Children from Sexual Offences (POCSO) Act, they said.