SK Srinivasan was attacked by a group of men at his shop in the heart of Palakkad town.
Two persons who allegedly carried out the murder of an RSS leader recently in Palakkad district, were arrested on Tuesday, bringing the total number of arrested accused in the case to 13, police said.
Police had a few days ago arrested a person who was also allegedly a member of the attacking party.
ADGP (Law and Order) Vijay Sakhare told PTI that of the 13 arrested accused, two were those who had identified the targets for the attacking party that had killed RSS leader S K Srinivasan (45) on April 16.
Besides them, three others were part of the six-member gang, he added.
ADGP Sakhare also said that all the 13 accused were either workers of or affiliated to the Popular Front of India (PFI) or its political offshoot Social Democratic Party of India (SDPI).
According to the police, their investigation so far has revealed that Srinivasan was killed in retaliation for the murder of PFI leader Subair (43) on April 15.
Police has also said that its probe in the two cases has also revealed that Subair was killed to avenge the murder of RSS leader Sanjith in Palakkad in November last year.
The PFI leader was allegedly killed by three friends of Sanjith.
ADGP Sakhare said today the test identification parade or TIP is to be carried out of the three RSS workers who allegedly carried out the PFI leader's murder.
Ramesh, a very close friend of Sanjith, along with two others had allegedly planned and also carried out the murder of Subair as he believed that the PFI leader was responsible for his friend's death.
ADGP Sakhare had earlier said those involved in Srinivasan's murder had initially made attempts to kill two other RSS leaders and on failing to find them, who had gone into hiding, they targeted Srinivasan.
Srinivasan, a former district leader and office-bearer of RSS, was attacked by a six-member gang at his motorbike shop in Melamuri near here on April 16, barely 24 hours after Subair was hacked to death at Elappully in the district while he was returning home along with his father after offering prayers in a mosque on April 15 afternoon.
The back-to-back killings involving BJP/RSS and SDPI/PFI is the second such incident in the past few months in Kerala.
In December last, a leader of the SDPI and a leader of the BJP were murdered in Alappuzha within 24 hours.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)