A case was filed accusing 50 identified BNP men and 1500 to 2000 unnamed ones over a clash between police and supporters of the party that left over 50 injured during a programme in Gangachara upazila of the district on Thursday. Law enforcers have so far arrested four BNP activists from different areas of the upazila since the clash. Hossain Raihan, assistant commissioner of police (ASP) of the district, confirming the  arrests said the case was filed accusing 50 named individuals and more than 1500 unnamed on Friday morning.  Sources said the upazila unit BNP called for a programme protesting the price hike of essential commodities and death of Jubo Dal activist Shaon during a clash with police in Narayanganj on September 1, in Puraton Sonali Bank intersection of the upazila on Thursday.   Read: Police-BNP clash: Ctg BNP convener, 74 others sued A clash broke out between police and the supporters of the opposition party following an interception by the law enforcers to the demonstrators on their way to Gangachara Bazar from the intersection around 4.30pm, sources and witnesses said. At one stage,  ASP Raihan said the BNP men pelted brickbats, and they retaliated with batons leaving over 50 people including cops injured. “The case was filed after scrutinizing necessary things so that no innocent is subjected to harassment,” he added.