The National Investigation Agency (NIA) in May filed a charge sheet in the special NIA court against Nainar Abbas Ali alias Appas Ali alias Library Abbas (28), M Samsun Karim Raja alias Karim alias Abdul Karim (23) and S Dawood Sulaiman (23).
It had claimed that the accused had formed an outfit, Base Movement, to further the objectives of banned terror group Al Qaeda.
The investigation revealed that the accused had carried out the Mysore court blast on August 1 last year as part of a "larger conspiracy" which included founding of the terrorist outfit Base Movement and carrying out various activities such as sending threatening letters to various jails, senior government functionaries, the Dinamalar's office and the French Consulate, and carrying out blasts at different court premises in South India, the NIA claimed.
The bomb blasts were carried out by the accused in five court complexes between April and November 2016, it said.
The accused have been booked under stringent provisions of the Unlawful Activities (Prevention) Act, the Indian Penal Code, the Explosives Substances Act and the Prevention of Damage to Public Property Act, the NIA said.