A red alert has been sounded and security stepped up at the Indira Gandhi [Images] International airport in New Delhi in the wake of unearthing of a terror plot to blow up an aircraft in the United Kingdom.

The airport security is entrusted to Central Industrial Security Force. Entry of visitors to the airport has been banned and emergency anti-hijacking measures put in place as the threat level at the high-security facility was raised to maximum, Central Industrial Security Force sources said.

Other measures taken include 100 percent manual checking of cabin baggage in "specific destination flights" and 50 per cent in normal aircraft besides increasing the profiling of passengers and deployment of security personnel in plain clothes.

Quick Reaction Teams deployed at the airport were activated, while Bomb Disposal Squads and sniffer dogs pressed into service as part of increased surveillance measures, they said.

Light-Machine Gun-mounted mobile patrols are patrolling non-operational areas, while surveillance was stepped up at parking lots and ticket counters. Airport authorities have also been asked to clear dust bins every half-an-hour and frisking of authorised personnel entering operational areas was made mandatory in view of the alert.

Airports across the country had been on a high alert as intelligence agencies reported the possibility of terrorist strikes to disrupt the Independence Day celebrations. Though there was only one specific intelligence input that the banned ULFA might strike at an airport in the north-east, a general alert was issued to airports in other regions as well earlier this month.

Onkar Singh adds -  "The Delhi police has been on high alert already and the level of vigilance has been further upgraded. But the airport security is not directly under us," Dr K K Paul, Delhi police commissioner, told rediff.com.