The five were involved in planting pipe bombs near Reliance Market at Uthangudi here and near the houses of former Union Ministers V Narayanasamy at Puducherry and P Chidambaram at Sivaganga few months back, a release from the DSP Q-Branch Police T Prabhakaran said.
They also allegedly printed pamphlets that instigated people against India.
The bombs would have caused loss of lives and serious injuries besides causing damage and destruction to properties had they exploded, the release said.
They also planned and conspired to carry out terrorist activities with the objective of getting separate Tamil Nadu, it said.