The incident occurred on Wednesday night when the girl was alone on the terrace of her house and the accused, who was on the terrace of the adjoining house, crossed over to her side and then raped her, Baghpat police station in charge K M Dohre said.
The girl has been sent for medical examination, he said.
On the basis of a complaint by victim's family, an FIR was registered against the youth yesterday, he said.
Efforts are on to nab the accused who is on the run, the official added.