The national capital was today wrapped in unprecedented security blanket for the 66th Republic Day celebrations which was graced by US President Barack Obama as the Chief Guest.
A seven-layer security ring has been thrown around the VVIP enclosure on Rajpath from where Obama, President Pranab Mukherjee, Prime Minister Narendra Modi and a host of other dignitaries witnessed the grand parade.
Central Delhi has turned into a virtual fortress with nearly 40,000 personnel drawn from Delhi Police and paramilitary forces guarding every nook and corner of the area.
More than 15,000 CCTV cameras installed have been relaying every movement live to a central control room where the footage has been monitored by a joint team of Delhi Police, US Secret Services and sleuths of central security agencies.
The three-km stretch of Rajpath has over 160 CCTV cameras - with one camera installed at every 18 metres.
Snipers and spotters of the National Security Guard (NSG) and Delhi Police have been deployed on all nearby high-rises which overlook Rajpath while dedicated radar monitored the air space.
Anti-aircraft guns have been put on standby to shoot down any aerial intrusion.
The Director General of Civil Aviation has issued a 'NOTAM' (Notice to Air Men) for diverting all flights flying over Delhi at the time of the parade.
Earlier, planes flying above 32,000 feet did not fall in the category of no-fly zone, but now the height has been raised to 35,000 feet, the sources said.
No plane will be flying within a radius of 400 km of Rajpath as against 300 km on earlier occasions, they said. This means airports adjoining Delhi like Jaipur, Agra and as far as Lucknow or Amritsar will not operate flights when the function will be on in the national capital.
For the first time, Airborne Warning and Control System (AWACS) has been deployed here on Republic Day for maintaining vigil from the skies during the parade.
While roads around Rajpath, India Gate and along the route of the parade till Red Fort have been blocked for vehicular movement, traffic restrictions have been put in place to ensure smooth movement of Obama's cavalcade.
Both carriageways of Sardar Patel Marg, which is next to ITC Maurya Hotel where Obama is staying have been completely shut down for normal traffic.
Snipers of Delhi Police and National Security Guards have been deployed at all nearby high-rise buildings near the hotel.
The green ridge opposite to the hotel has been thoroughly checked and police personnel have been deployed in the forested area along the ridge till the US President leaves the Capital tomorrow.
Security agencies have also sealed 71 buildings in close proximity of Rajpath which is the Republic Day parade route. Security personnel have been deployed on rooftops.
Even bonafide citizens of Lutyens' zone, including MPs and officers of the Armed Forces, have been either issued special passes or have to establish their identities to enter the zone.
Police have also installed around 80 face-recognition cameras around the venue of Republic Day celebrations and at the city's entry points to identify any subversive or criminal elements.
Spectators have been made to pass through a stringent multi-layered security check to be able to watch the parade and they were not allowed to carry any electronic gadgets to the venue.
The 80,000-strong Delhi Police force assisted by another 20,000 drawn from para-military forces and state armed police were on vigil for last few days to prevent any untoward incident in the city.
Specialised canine units of Indian paramilitary forces were deployed along with team of seven Belgian 'Malinois' dogs of the US Navy Seals which are accompanying the security personnel of the US.
Known as 'canine officers', their breed shot to limelight following Operation Neptune Spear where they sniffed out and helped in the arrest of most wanted terrorist Osama Bin Lade from a house in 2011 in Abbottabad in Pakistan.
These canines are deployed to secure ITC Maurya along with a dozen canines of the Indo Tibetan Border Police.