Filmmaker Anurag Kashyap has filed a police complaint after a person allegedly sent him a threat on micro-blogging site Twitter, an official said on Saturday.
The official termed it as an "abusive one line general threat" and said Mr Kashyap had registered the complaint at Cyber police station of the Mumbai Crime Branch.
"The threat was made on Thursday. We have started a probe," he said.
Mr Kashyap was among the film personalities who, on July 23, wrote an open letter to Prime Minister Narendra Modi asking him to intervene in incidents of lynching and the alleged weaponisation of the slogan "Jai Shri Ram" into a "war cry".
Only a few days ago, actor Kaushik Sen, also a signatory to the letter, claimed to have received death threats.
"Yesterday I received a call from an unknown number, where I was threatened of dire consequences if I don't stop raising my voice against lynchings and intolerance. I was told that I would be killed if I don't mend my ways," Kaushik Sen, 50, had told news agency news agency Press Trust of India.
Mob attacks, like those that killed Tabrez Ansari, 24, in Jharkhand last month, were brought into sharp focus by the authors of the letter, who argued "human lynching is our concern. Our objection is against lynchings be it against Muslims or Hindus".
"Dear Prime Minister... The lynching of Muslims, Dalits and other minorities must be stopped immediately. You have criticised such lynchings in parliament Mr Prime Minister, but that is not enough... We strongly feel that such offences should be declared non-bailable..." the letter said.