About 150 Indians, most from the southern states of the country, have been actively engaging with Isis supporters and following the Islamic State's propaganda, intelligence agencies have warned.
The Indian Home ministry had said this week that Isis attacks are possible in India and that the terror group has been able to radicalise many youths in the country.
India issued a country-wide alert for possible Isis attacks after the group unleashes a series of terror attacks in Paris last week, killing 129 people.
While at least 20 Indians have already joined Isis in Iraq and Syria, nearly 150 Indians in the country have been actively following the group's activities and propaganda and are under watch by intelligence agencies, as per reports.
A majority of these Isis followers are said to be based in the southern states.
Intelligence agencies are said to be keeping a close watch on the individuals leaning towards Isis to check if they are radicalised to join the group.
"Most of the persons under surveillance have been in regular contact with some ISIS activists online. Hence, we kept all of them under surveillance," an official was quoted saying by the Press Trust of India.
The Home Ministry had said that the threat of Isis attacks in India comes from the Islamic State's "success in radicalising some youth and attracting certain sections of the local population or Indian diaspora to physically participate in its activities, or the possibility of piggy-backing on terrorist groups operating in India".
Under the guidance of the National Technical Research Organization (NTRO), these intelligence agencies are now tracking Isis-related traffic online.