At least three alleged sympathisers of extremist group Islamic State in Iraq and Syria (ISIS) have reportedly been arrested from three different locations in Karnataka and Maharashtra.

A joint team of Maharashtra Anti-Terrorism Squad and National Investigation agency arrested an ISIS suspect from Mumbra, a suburb of Thane district, on Friday morning, Zee News reported.

Two other ISIS sympathisers, identified as Najmul Huda and Syed Hussain, were arrested in Karnataka, a journalist with NewsX channel said in a tweet.

While Huda was arrested from Mangaluru, Hussain was taken into custody from Tumakuru, located about 71 kms from state capital Bengaluru.

The surveillance across India has been tightened over the terror threats it has received in the wake of the 67th Republic Day. French President Francois Hollande will attend the Republic Day celebrations as the chief guest this year.

Earlier this week, the Delhi Police arrested a suspected militant along with his three accomplices from Roorkee for allegedly planning an attack at Ardh Kumbh Mela in Haridwar, Uttarakhand. It was later revealed that they had links with ISIS.

All the four suspects were sent to police custody for 15 days on Tuesday.

Last week, the Goan State Secretariat received a letter threatening to kill Prime Minister Narendra Modi and Defence Minister Manohar Parrikar, with "ISIS" written at the bottom.