Ashok Sahu approached the parents of the victim Tuesday to locate the address of a resident in the city's Salia Sahi slum.
The family sent the Class 4 student to lead him to the house, Anup Kumar Kanungo, inspector in charge of the Nayapalli police station in the area, told IANS.
Instead of locating the house, Sahu allegedly took the girl to a secluded area of the slum and raped her.
He strangulated her to death in an attempt to destroy evidence, Sahu said.
The incident occurred Tuesday afternoon, but came to light after the victim's family and other residents looked for the girl when she did not return.
The residents spotted her body lying in a nearby ground, and informed police.
It was a close circuit camera placed at the gate of a private college that showed the accused leading the victim away.
Locals nabbed Sahu and handed him over to the police.
The victim's family and the accused are daily wage earners and residents of the same slum. They were known to each other before the crime, the police official said.
The child's body was sent to Capital Hospital for post-mortem examination.
As news of the crime spread, over hundred activists of the opposition Congress and Bharatiya Janata Party and women's organisations reached the hospital and ransacked the premises.