The national capital was today brought under an unprecedented ground-to-air security cover with thousands of armed personnel keeping a tight vigil for the 67th Republic Day celebrations where French President Francois Hollande was the chief guest.
The area around Central Delhi was turned into virtual fortress in view of intelligence inputs that terror groups may target some important installations in the city.
Ahead of the Republic Day celebrations, central security agencies and NIA busted a module by arresting 14 militants linked to terror group ISIS.
The group had planned to carry out sensational strikes at important installations and its members had also visited the national capital, official sources said.
Commandos with light machine guns were deployed at 10 strategic locations and anti-aircraft guns remained positioned at two vantage points in the capital.
The entire region of Central and New Delhi had nearly 50,000 security personnel drawn from Delhi Police and central security forces guarding every nook and corner.
Special arrangements were made at the historic Rajpath where India's military might was on display. Hollande was seated along with Mukherjee and host of VVIPs including Vice President Hamid Ansari and Prime Minister Narendra Modi.
The enclosure of the VVIPs was put under a multi-layer security ring with Presidential Guards and officials of SPG and NSG guarding the two inner-most orbits and Delhi Police entrusted with guarding the outermost circle, said a senior official.
Special patrolling teams, comprising three officials including a commando, were deployed in New Delhi area within two-kilometer radius from India Gate.
Senior officials said snipers have been put on 45 buildings overlooking Rajpath besides providing a similar cover along all the buildings along the parade route.
Gunners have been given clear instructions to bring down any aerial object flying without permission. A 'NOTAM' (Notice to Airmen) has been declared from 10.35 AM to 12.15 PM during which no flights will land or take off at the Indira Gandhi International Airport.
"Specially trained police personnel with light machine guns have been deployed at 10 strategic spots in New Delhi area," a senior police official said.
Officials said anti-aircraft guns have been deployed at two vantage points to ward off any threat from the sky.
A special control room has been monitoring as many as 15,000 CCTV cameras installed across Central and New Delhi, with 200 high-tech digital cameras installed in the parade route, an official said. As many as 1,000 traffic officials have been issued revolvers so that they can deal with any untoward incident amid heavy security arrangements across the city involving around 25,000 police officials.
The airspace will remain out of bounds for commercial flights arriving and departing out of the IGI airport here between 10.35 AM and 12.15 PM tomorrow. "Around 60 arrivals and departures take place at the IGI airport during this period, for which the notice was issued by the Airports Authority of India," a senior official said.
Meanwhile, Delhi Police has set up a wireless integrated public address (WIPA) system to enhance security at crowded places and popular markets in the city. WIPA is a centralised public address system now installed at 31 crowded places and markets in Delhi, and also in 13 major metro stations.
The national capital is already on high alert after inputs were received about the presence of key members of several terror groups in Delhi.
In an inter-state coordination meeting held earlier this month, Delhi Police Chief B. S. Bassi had asked his force and police departments of neighbouring states to keep a vigilant eye on drones, as they have been perceived as a major threat to security, said a senior police official.