NEW DELHI - The Indian capital's international airport was the scene of a major security scare overnight Thursday but no incidents have been confirmed, a security official at the airport told AFP.

"We have combed the airport inch by inch and we have found nothing. The same is for the domestic airport. Nothing has happened," said K. R. Singh, an official at the Central Industrial Security Force (CISF) airport control room.

The CISF is the paramilitary unit responsible for airport security.

"All our men are still searching but have found nothing. We have no incident," he added, rejecting unconfirmed media reports of a shooting incident at Indira Gandhi International Airport.

The NDTV news channel reported that three shots were fired from a car at the airport, and that security forces were trying to trace the vehicle. It gave no further details.

India had put its airports on high alert Thursday following warnings of possible attacks using hijacked aircraft, officials said, a week after Islamist militants launched a devastating assault on Mumbai.

The emergency measures were enacted as Defence Minister A.K. Antony ordered the armed forces to be on guard against "any terror strikes from the air."

All major airports -- including Bangalore, Chennai, Hyderabad, Kolkata, Mumbai and New Delhi -- were placed on high alert.

The Press Trust of India said an attack may be timed to coincide with the December 6 anniversary of the destruction of the Babri mosque in northern India by Hindu extremists in 1992.