A complaint in this regard was lodged by Lal Singh Rajput, a Shiv Sena activist from suburban Kandivali, said police.
According to police, one of Rajput's friend had posted a comment about Amarnath terror attack wherein he had appreciated the stand taken by the late Sena chief on terrorism.
However, the accused, aged 17, posted some objectionable comments in response to the post against the Sena founder, the official said.
A case under section section 295 (A)(malicious acts intended to outrage religious feelings or any class by insulting its religion or religious beliefs) of IPC has been registered against the accused, the official said.