Muralidharan, the former vice-chairman of Thaliparamba municipality, is the first accused in the murder of Muslim League leader K V M Kunhi, police said.
A total of five accused, including Muralidharan, were arrested today, they said.
Another accused T Prakashan also took oath as municipal councillor.
While Muralidharan absconded after incident, Prakashan, arrested earlier and remanded by the court, had sought its permission to take oath, they added.
K V M Kunhi (55) an IUML activist, who had been seriously injured in a post poll clash between CPM and IUML workers near Thaliparamaba on November 2, died without responding to treatment at a private hospital on November 4.