A BJP supporter died when party workers clashed with police while protesting the arrest of five persons on charges of cow smuggling in Narhi area of Ballia district.
While the protesters alleged that the worker died in police firing, police have denied the charge.
Heavy police force has been deployed to bring the situation under control and cases have been registered against BJP MLA Upendra Tiwari, 35 named and 300 unnamed accused under various sections of IPC and six persons have been arrested.
Superintendent of Police Manoj Kumar Jha said the MLA and his supporters sat on dharna before Narhi police station and clashed with police last night in protest against the arrest
and pelted stones when authorities tried to evict them.
Police then lobbed teargas shells and fired rubber bullets to disperse the irate crowd, he said.
District BJP chief Binod Dubey alleged that police used batons and opened fire at the party workers leading to the death of Vinod Rai and injury to 50 others.
However, Jha refuted the charge saying the worker did not die in firing as police did not open fire and said the reason behind his death would be known only after getting postmortem report.
Though the SP said the MLA was absconding, Dubey claimed that he was seriously injured in the police action and was undergoing treatment in a hospital.
Heavy police force has been deployed to bring the situation under control and a magisterial inquiry has been ordered into the incident.