With Mumbai train blasts fresh in mind, massive security arrangements have been chalked out for the main Independence Day function to be attended by Prime Minister Manmohan Singh and top leaders.
Red Fort, from whose ramparts the Prime Minister will address the nation, has already been sealed off with a multi-tier security apparatus being thrown in and around the historic monument.
Hundreds of Delhi Police personnel have taken over the majestic monument and the premises is being sanitised for the national event. Army mine-sweepers and bomb-disposal squads have begun scanning the Red Fort premises.
To check alertness of the security personnel deployed there, "mock penetration" drills are being conducted, police sources said.
With the security threat high on their mind, measures like aerial surveillance by policemen in choppers, deployment of Air Defence Guns and positioning of Quick Reaction Teams (QRTs) of commandos will be put in place to ensure that the function passes of peacefully.
A select group of over 500 Delhi policemen and commandos from the paramilitary forces will exclusively guard the Prime Minister, providing him the second ring of protection, while he unfurls the national flag and addresses the nation from the ramparts of the majestic monument.
Surprise searches and verification in the walled city and adjoining areas have also been launched.
A close watch is being kept at visitors to guesthouses, hotels and other places in the capital to prevent any terrorist from taking shelter.
Elite commandos of the Delhi Police have also been deployed at high-rises in the vicinity of Red Fort as part of efforts to thwart the use of long-range weapons.
The Capital will be made a 'no-fly zone' during the function, expected to last for nearly 45 minutes, and trains passing near the venue will not be allowed since early morning till the function concludes.
A tight vigil will also be maintained at the samadhis of various national leaders, where the Prime Minister and other top dignitaries will pay floral tributes before proceeding towards the Red Fort.
Security will be "extremely tight" across the capital on the day in the wake of a general threat perception, though senior police officials said they have not yet received any specific threat to disrupt the function.
Police have also launched an exercise to identify vehicles stolen in the capital in the last few months as a security precaution.