Police got a tip off on the plot when they dispersed a crowd which prevented the Dalit leader's entry to Vadacheri village.
Acting on it, a 12 member gang which conspired to hurl petrol bombs at Tirumavalavan at Alathur was arrested, police said.
The attempt to attack comes against the backdrop of heightened tensions in Villupuram district following clash and consequent violence between two communities.
CPI state Secretary G Ramakrishnan and TNCC president E V K S Elangovan in separate statements, sought immediate arrest of the culprits.