Police sources said seven right-wing activists have been taken into custody for the attack.
Several instances of violence between CPM and BJP activists were reported from across Kerala on Sunday.
In the capital Thiruvananthapuram, two CPM activists have been hospitalised after being injured in a clash between supporters of the two parties that took place during a protest march by the Left activists.
Earlier in the morning, CCTV footage accessed by police showed two Social Democratic Party of India workers on a two-wheeler attacking a CPM worker in rural Thiruvananthapuram. The CPM activist identified as Shashi Kumar has been hospitalised.
Late into the evening, a CPM office was attacked. Police sources said seven right-wing activists have been taken into custody for the attack. A right-wing labour union office of the Bharatiya Mazdoor Sangh was also attacked by a gang of men on six motorcycles.
In Kannur, four Rashtriya Swayamsevak Sangh activists were attacked with iron rods by unidentified men, according to police sources. Two of them have been hospitalised with head injuries.
In another incident in Kannur, a CPM branch secretary has been hospitalised after a country-made explosive was thrown near a CPM rally venue.
Incidents of political violence in Kerala have grabbed national headlines across the country in recent months with both left and the right-wing outfits accusing eachother of increased hostilities.
Kerala has a long history of political violence. Police records of political murders between 2000 and 2017 impugn both the left and right-wing fronts. In the last 17 years, 85 CPM workers, 65 RSS or BJP workers, 11 workers of Congress and IUML each have been killed - mostly by their political rivals including CPM and RSS or BJP.