The National Investigation Agency (NIA) on on Sunday midnight picked up three youths from Madurai for their suspected terror links.
In raids in several places, three suspected Al Qaeda operatives were on Monday arrested by the National Investigation Agency.
Police said the three allegedly planned to attack 22 top leaders of the country including Prime Minister Narendra Modi. They were allegedly involved in threatening embassies of various countries in India, they said.
They have been identified as M Khareem, Asif Sultan Mohammed and Abbas Ali. While Khareem was arrested from Usmannagar, Asif Sultan Mohammed was picked up from GR Nagar and Abbas Ali from Ismailpuram, police said.
Police said NIA raided several places on specific information that suspected Al Qaeda activists were operating from South Tamil Nadu in and around Madurai.
"Explosive materials and arms have been seized from them," police said, declining to elaborate.
Certain digital devices like mobile phones and hard discs were also seized from the three suspects arrested by NIA.
The trio was allegedly running the Al Qaeda unit in South Tamil Nadu. They were also allegedly involved in the explosions that took place in various courts in the country over a period of time, police added.