The national capital has turned into a virtual fortress two days ahead of Independence Day with over 6,000 security personnel on duty to pre-empt any terrorist strike in the city.

Considering central intelligence inputs that terror group Lashkar-e-Taiba may attempt to attack markets or places of strategic importance, an impregnable ground-to-air security apparatus is being put in place at Red Fort and areas within its five-kilometre radius.

Intelligence agencies have warned Delhi Police that the terrorists may effect a strike like the recent Gurdaspur or Udhampur attacks.

A multi-layer security apparatus will be in place around the 17th century Mughal monument Red Fort from where Prime Minister Narendra Modi will unfurl the Tricolour and address the nation for the second time on Saturday.

An official said they have arranged special security for the prime minister as he is at the highest risk of a terror strike as compared to other VVIPs.

"A designated team of over 150 National Security Guard (NSG) commandos along with SWAT (Special Weapons And Tactics) unit and paramilitary forces will be positioned in the radius of 200-metre from the ramparts of the fort to guard the prime minister," the official told IANS on the condition of anonymity.

"The commandos will be equipped with fully automatic weapons, high-tech communication gadgets, body armour, protective helmets and other security measures. They are experts in handling multiple attacks at the same time," he said.

Besides sky patrols by helicopters, an air defence mechanism will also be put in place around the venue.

Security personnel along with sharpshooters of the NSG will be placed on all high rise buildings around the Red Fort from Friday.

"Over 500 CCTVs have been installed in and around the Red Fort to keep a close watch on the area. A central control room has also been set up at Red Fort to constantly monitor the situation," the official said.

Some ultra high-resolution cameras have been mounted on the towers of the fort to keep tabs on any suspicious activity within a 5-km radius of the historic monument.

At least 80 companies of security forces (about 6,000 personnel) from Delhi Police and paramilitary forces will be deployed at the Red Fort and the surrounding areas during the Independence Day celebrations, said the official.

The official said that the localities around the Red Fort have been sanitised and informers deployed to keep a check on movement of suspicious people.

Thousands of Delhi Police personnel and paramilitary have already been deployed at market places, airport, railway stations, inter-state bus terminals, metro stations and places of strategic importance.

Netaji Subhash Marg, S.P. Mukherjee Marg, Chandni Chowk Road (from Fountain Chowk to Red Fort), Nisad Raj Marg and Link Road will be closed for general traffic from 5-9 a.m. on Independence Day.

Police said only labelled vehicles will be permitted.