Five CPI(M) workers and an equal number of police personnel were injured when a procession of the Left party workers was attacked at Kaivellikal, allegedly by RSS workers, who threw country bombs and stones at them, the police said.
Though bombs were also hurled, the injuries were a result of stone-pelting, they said, adding that the injured were admitted to a co-operative hospital at nearby Thalassery.
The CPI(M) alleged that RSS activists were behind the incident.
The ruling party in Kerala has called for a 12-hour hartal in the area tomorrow to protest against the attack.
Additional personnel had been deployed in the area as a precautionary measure, the police said.
Kannur, a politically volatile district in Kerala, has a history of clashes involving CPI(M) and BJP-RSS workers.