The victim, a class IX student, was in relationship with a boy from his lane in Sri Ram colony, Police said.
They said the girl's family was against her relationship with the youth and her brother had reportedly reprimanded her for meeting the 20-year-old on August 30.
On the evening of the same day the girl again went to meet him near a temple from where she went missing, said a senior police officer.
Police found her body from there on September 1.
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The family members of the victim had registered a case at Khajuri Khas police station. They suspected a youth from their lane was behind her disappearance.
While police were trying to trace the girl, her family received calls from an unknown number and the caller said she was in Firoz Shah Kotla area and later the caller said she was in Yamuna Vihar area.
The accused allegedly tried to force himself on her but later strangulated her as she resisted, police said.
During investigation, police put the number which was used to call the victim's family, on surveillance. The accused was located in Loni area from where he was arrested.
The post-mortem report revealed strangulation as cause of death, police said.