Security has been ramped up in the national capital with police barriers put in place across the city, the officer added.
Heavy police deployments have been made in areas within a 3 km radius of the Red Fort from where Prime Minister Narendra Modi will address the nation on Thursday morning to mark the 73rd Independence Day of India.
"Intensive checking drives have been initiated at the airport, railway stations, Metro stations, bus stops, markets, malls and the border areas," the officer said.
Also, verification of tenants, servants, occupants of guest houses, dealers of used scooters and cars and cyber cafe users is in full swing across the capital.
"There shall be special multi-layer checking of all vehicles, both private and commercial, entering the city from neighbouring states through border entry points," a senior police officer said.
"An alert has been issued by the intelligence agencies regarding terrorist outfits planning to carry out strikes across the nation and near the Red Fort. The Bureau of Civil Aviation Security has written to all state police chiefs, directing them to make adequate security arrangements in their respective states," the officer added.
Besides officers of the Delhi Police, security officers in plain clothes, snipers, National Security Guard (NSG) personnel, the Army and SPG commandos as well as ground to air surveillance will be deployed around the Red Fort.
At least 80 companies of security forces (around 6,000 personnel) will be deployed at the Red Fort and the surrounding areas, said the officer.
Delhi Police and Delhi Traffic Police personnel will be spread out across the city to secure important places as well as for manning entry and exit points at "vulnerable locations". All high-rises, hotels, guest houses, markets and restaurants in Paharganj, Jama Masjid and the areas surrounding the Red Fort will be under the police scanner.
Even rickshaw-pullers and vendors in the area have been asked to keep a lookout for suspicious objects and people, the police said.
"We have also received a letter from the Intelligence Bureau about a possible threat from a terrorist outfit ahead of August 15," a police source told .
"All the neighbouring states have also been alerted and security has been beefed up at the border check-posts, railway stations, Metro stations and all interstate bus terminus," said a senior officer.
According to sources, more than 1,500 CCTV cameras have also been installed near the sensitive places.
"Several check points and door frame metal detectors (DFMD) have been installed at all the entry points. Facial recognition cameras have also been installed to capture and identify any possible suspect," said Nupur Prasad, Deputy Commissioner of Police (DCP).
"There are intelligence inputs that some terrorists holding Afghanistan passports may enter the national capital on medical and tourist visa. We are taking adequate measures to quash any untoward incident," the officer added.
Delhi Traffic Police have put in place several traffic restrictions for the general public. The restrictions will be in place on Thursday as well.
An advisory has been put up on Delhi Traffic Police's Twitter handle with an elaborate map of the possible routes that can be taken.
( With inputs from IANS )