An anonymous e-mail threatening to blow up the international airport here has prompted authorities to step up security by deploying additional forces inside and outside the facility.

The information about the e-mail was passed on to higher officials of the CISF, which is handling security at the Indira Gandhi International Airport (IGIA), from Gujarat, CISF sources said.

The airport has been on high alert since terrorists struck Mumbai on Wednesday night killing over 180 people and security was strengthened in the facility by intensifying checking and patrolling.

Sources said the CISF deployment inside the airport has been increased after the Mumbai terror attacks while Delhi Police had been roped in to provide more security to the facility.

"We have taken adequate precautions after receiving information about an email threatening to blow up the airport.

There is nothing to panic. We are leaving nothing to chance.

Adequate steps have been taken," a senior CISF official said.

The security establishment has also asked CISF to coordinate with Delhi Police to provide security to the 'city side' of the airport, which is outside the terminal building.

Fearing attack on aircraft, Delhi Police have already prohibited assembling of people or parking of vehicles at a 500-metre stretch on the NH-8 near the airport.

The order came in the wake of reports that a large number of people gather near the landing and take off area of the airport which may cause security risk for the aircraft.