They said the arrests were made after a raid near Vallapuzha railway gate here early this morning.
Tension has been prevailing in the region for some time between the party workers after results of the May 16 Assembly results were out.
The clashes had begun last week when a CPI(M) activist was attacked by a group of BJP workers.
A library building was vandalised and several vehicles damaged in the attack, police said, adding a number of minor incidents of clashes had occurred in the region soon after.
The clashes had gained media attention after CPI(M) leader and Shornur MLA PK Sasi publically admonished a police official over the recurring political violence in the region, kicking up a storm.
The MLA had alleged that police was extending support to RSS activists and not showing interest in booking the culprits.
The video, showing the MLA warning the police publically, had gone viral and triggered widespread protests, prompting him to tender an apology today