Many states, especially Delhi, Jammu and Kashmir and the Northeast, were put under an intense security blanket ahead of the Republic Day on Sunday, amid terrorist threats to disrupt the 54th annual celebrations.

Intelligence reports have suggested that terrorists might use a small plane or other flying objects to carry out strikes, prompting the Air Force bases at several paces across the country to be on standby.

Intelligence agencies have warned that terrorists from Al-Qaeda, Lashker-e-Tayiba, Al Badr and Jaish-e-Mohammed outfits may try to attack the parade route, Delhi Airport or the recently-launched Metro Rail.

New Delhi, where the main parade would be held and watched by the country, including Iranian President Mohammad Khatami, is under tight security.

While two Indian Air Force helicopters would hover over the nine-km parade route from Vijay Chowk to Red Fort, 25,000 personnel from the Delhi Police and central paramilitary forces have been deployed on ground.

Nearly 800 elite commandos from the National Security Guard, Indo-Tibetian Border Police and Delhi Police, Quick Reaction Teams of police, Hazmat vans [to tackle a Nuclear, Biological or Chemical attack] would be positioned at various strategic places.

High-rise buildings flanking the parade route have been taken over by the security forces and sharpshooters stationed there.

Flight operations at Delhi airport would remain suspended between 1130 hours and 1215 hours IST and rail traffic would be stopped between 1030 hours and 1200 hours IST.

Jammu and Kashmir too have been put on high state alert as terrorists have issued statements threatening to carry out attacks on Sunday.

A multi-layered security has been put in place in Jammu, where the main function would be held in Maulana Azad Stadium. The venue has been sanitised and surrounding buildings taken over the security forces.

Army, paramilitary forces, and the local police will maintain a three-ring security apparatus.

All the Northeastern states have also been put on high alert with security forces being deployed at vital and vulnerable places and patrolling intensified.

A special alert has also been sounded in West Bengal, particularly along the Indo-Bangladesh border.

Security measures were tightened in and around the historic Gandhi maidan in Patna in Bihar where the state's main function would take place.