Those arrested have been identified as district Secretary of the Tamizhar Desiya Makkal Katchi Tiruselvan, Tamilarasan and Kaviarasan, a senior police official said.
Two country-made bombs with wicks, two pipe bombs and six gelatin sticks have also been recovered from the hide-outs of one of the accused at Villapuram.
Besides three knives, two laptops, petrol can and some literatures relating to Tamizhar Makkal Viduthalai Iyakkam, a freedom movement, from the house of another accused at Melur, they said, adding notices similar to those seized on February 10, where the bomb was planted, have also been recovered.
Police said further investigations were on to find out from where they had received the bombs.
A similar type of bomb was recovered from outside the residence of Union Minister V Naryanasamy on January 29, Rajaram said.