A 52-year-old teacher of a government school in north Delhi's Burari was arrested for allegedly sexually abusing his 15-year-old student, police said.
The incident came to light after a video of the act was forwarded by the teacher to an acquaintance who made it viral with an intention to blackmail the accused, a senior police officer said on Saturday.
The incident came to light on Friday following which the teacher was arrested, the officer said, adding it was suspected that the video was shot in June.
The police were probing whether the accused had abused other students and how long he had been abusing the victim.
The victim stays with his family in northwest Delhi's Swaroop Nagar.
The parents of other students staged a protest outside the school today demanding strict action against the teacher. Earlier this month, an electrician was arrested for allegedly raping a Class 2 student in a New Delhi Municipal Council School.