The incident occurred when ABVP workers protested against a programme organised by CPI(ML) on the JNU controversy in front of Muzaffarpur Municipal Corporation's (MMC) auditorium, a senior police officer said, adding that the Left workers raised the slogan 'Main JNU Bol Raha Hoon'.
As ABVP workers protested against the sloganeering, both sides started pelting stones, he said, adding the incident left four persons injured.
While two of them sustained injuries on their head, two others received leg injuries.
MMC Commissioner, Ramesh Prasad Ranjan said that earlier CPI(ML) had asked for permission to hold a programme for intellectuals in support of Jawaharlal Nehru University (JNU) at the auditorium but ABVP workers objected to the proposal.
The Commissioner cancelled the venue of the programme after he did not get any update from the CPI(ML) workers.
However, CPI(ML) workers decided to hold the programme in front of MMC's auditorium which falls under Mithanpura police station area of the town.