An FIR (First Information Report) was lodged in Bihar's Muzaffarpur on Thursday against nearly 50 celebrities, including Mani Ratnam, Ramachandra Guha and Aparna Sen, who had written an open letter to Prime Minister Narendra Modi raising concern over the growing incidents of mob killing, police said.

The case was lodged after an order was passed by Chief Judicial Magistrate Surya Kant Tiwari two months ago on a petition filed by local advocate Sudhir Kumar Ojha.

"The CJM had passed the order on August 20, accepting my petition upon the receipt of which an FIR was lodged today (Thursday) at the Sadar police station," Mr Ojha said.

The letter was written by 49 eminent personalities, including filmmakers Mani Ratnam, Anurag Kashyap, Shyam Benegal, actor Soumitra Chatterjee as well as vocalist Shubha Mudgal in July this year.

It had said that the mob killing must be stopped immediately while stressing that there was "no democracy without dissent".