The Indira Gandhi International airport here was shut down for nearly 20 minutes following reports of gunshots near the arrival terminal early Friday.

The alarm was raised reportedly after a white Qualis car tried to approach the arrival terminal from the opposite and restricted direction around 1.10 a.m.

Vibhash, a 25-year-old employee of the Le Meridian hotel told reporters that he heard at least two gunshots from the direction of the unidentified Qualis car bearing Haryana registration number.

"I have not seen any one firing but definitely heard sounds similar to gunshots," he said.

Unconfirmed reports suggested that two police vehicles were on hot pursuit of the car.

The control room of the CISF received a call at around 1.10 am from passengers that they heard sound of gunshots from one of the gates of international departure lounge of the airport, official said.

"We received a call that some passengers heard a sound similar to two gunshots, but there were no eyewitnesses. No evidence has so far come up to suggest that it was a firing and we cannot confirm it as a gunshot," Udayan Banerjee, DIG, CISF and incharge of security at Delhi airport told PTI.

"After the sound, the CISF and Delhi Police deployment swung into action and intensified the checking at the airport," he said adding the passenger movement is normal and arrival and departure is also functioning smoothly.

Following the reports of gunshots, officials of the Central Industrial Security Force and Delhi police, both responsible for the security at the airport, swung into action and surrounded the airport.

The gates of the airport were immediately closed and intensified searches were launched.

"We have carried out the intensified searches but have not come across any suspect. Additional security personnel are already deployed at the airport in the wake of terror threat to blow up three major airports in the country," said a CISF official deployed at the airport.

"We are taking every precautionary measure and there is no need to panic," he added.

Three international flights were delayed because of the incident. However it could not be confirmed.

Delhi police spokesperson Rajan Bhagat said, "a call was received that three to four rounds of firing has taken place at the airport but no one was injured."

"We are not yet sure whether any firing actually took place. We are verifying the facts," Bhagat added.

CISF officials said all preventive measures have been taken and a security drill has been put in place.

Airports across the country were yesterday put on high alert in the wake of intelligence reports that terrorists from Pakistan or Afghanistan may strike using a hijacked aircraft even as the Indian Air Force said it was ready to counter a 9/11-type aerial attack on New York.

Additional contingents of CISF and police inside and outside the Delhi airport has already been deployed, authorities said.