The police said in the first incident, the victim was recovered from the park after pedestrians heard her screams.
The accused juvenile was subsequently arrested.
According to the police, the sexual assault occurred minutes after the victim, a resident of the Trilokpuri area, was lured away by the accused while she was at play outside her house at around 9:30pm.
"He was loitering in the area when he spotted her. When he realised there were several people in the vicinity of the park, the enraged juvenile, who was not successfully able to rape her, left her howling in pain and fled," said an officer.
The police were informed and the victim was rushed to the Lal Bahadur Shastri (LBS) Hospital where she was admitted and a medical examination did not confirm sexual but confirmed physical assault.
Since rape could not be medically established, a case under relevant sections of Protection from Children from Sexual Offences (POCSO) Act, 2012, has been registered at the Mayur Vihar police station and the suspect has been sent to an observation home.