An RSS worker was stabbed to death in Pappinissery, in the Kannur district of Kerala on Monday night.
Sujith, 27, was attacked at his house, along with his relatives, who also suffered injures, after 10 people forced their way in.
Though he was rushed to a hospital, he succumbed to his wounds.
Police have arrested eight CPI (M) workers in the case so far. BJP has called for a hartal in Kannur district on Tuesday.
While CPI-M has described the incident as a fallout of a local issue of insulting a girl, BJP leaders in Kannur have alleged that CPI-M was behind the attack to get over the embarrassment of arrest of Kannur district secretary, P Jayarajan, in a murder case.
State Secretary Kodieryi Balakrishnan said the attack was not political and was a purely local issue and had nothing to do with the CPI-M.
BJP state President Kummanam Rajasekharan said the attack cannot be considered an 'isolated' incident.
"In Kannur, the attacks on BJP and RSS are a continuing affair. This is not an isolated incident," he said.
Some attacks at BJP leadersâ€™ houses have also been reported from the district.
The police have deployed a large number of personnel to the district following the attacks.