The Muslim radicals had attacked the professor as a punishment for the alleged reference to Prophet Mohammed in a question paper that he prepared for an internal exam in 2010.
The two accused, who hailed from Thalassery, were handing out pro-Maoist pamphlets and shouting pro-Maoist slogans when they were arrested from the Pantheerankavu market.
NIA has filed a charge-sheet against 11 accused persons with links to Khalistan terror, including a British national in connection with the murder case of Punjab unit RSS vice-president Brigadier Jagdish Gagneja
The NIA officials stated that Tamil Nadu tops the list of Indian states where anti-terror agencies have unearthed modules of Salafi jihadi terrorist organization IS over a period of five years since 2014.
Tiwari, a former Hindu Mahasabha leader, was assassinated at his Lucknow office by one Ashfaq and one Moinuddin who are still absconding and on the run.