UPDATE 17:32 IST: The four men have reportedly confessed to plotting bomb blasts on Haridwar-bound trains, NDTV reported.
The four men arrested by the Delhi police on Tuesday for planning an attack at the Kumbh Mela in Haridwar had links to the Islamic State in Iraq and Syria (ISIS), the police said.
The four men were also reportedly planning attacks at several prominent points in Delhi.
They were arrested from Roorkee in Uttarakhand on Tuesday night. All four suspected militants were in touch with their handlers in Iraq and Syria through Facebook and WhatsApp, The Times of India reported.
Indian intelligence agencies have warned of a possible ISIS attack in the country, especially during the 67th Republic Day on 26 January.
Akhlaq ur-Rehman, one of the arrested men, had also been questioned on the Pathankot Air Force base terror attack, NDTV reported.
They were sent to 15-day police custody on Wednesday.
Security has been beefed up at the Ardh Kumbh Mela in Haridwar following the terror threat, the Press Trust of India reported.
The Centre has also asked all states to remain on high alert on Republic Day, following 'lone wolf' ISIS attacks threats.