The activists were protesting against the arrest of 29 persons, including Ex-MLA Rajaram Singh, during which they clashed with the policemen and pelted stones at them in which the policemen were injured, the police said.
The injured policemen, including three women, were admitted to hospital, they said.
The police later lathicharged on the protesting CPI(M-L) workers to disperse them, the police said.
The police had arrested 29 persons on May two last following an incident of violence and arson by a mob, comprising local people and opposition workers to protest the murder of Sonhathu panchyat mukhiya Devendra Singh alias Chhotu by the armed assailants on March 29 last.
The CPI (M-L) and other opposition parties have demanded a CBI probe in the mukhiya's murder and the police lathicharge on the protesters.