NAIA General Manager Edgardo Manda said law enforcement agencies are helping to secure the airport against the terrorists from unspecified countries.
The airport chief placed NAIA on double red alert after the intelligence community informed him that "external elements" were planning to bomb the airport.
"Before, it was internal. Now our intelligence people are saying that the threat is coming from outside," Manda said, citing intelligence reports he classified as "A-1."
"Apparently, there are terrorists who have something to with the Abu Sayyaf," he said, noting the bandit group has sympathizers from "radical Muslim states" which he however refused to specify.
He said airport authorities have beefed up round-the-clock security at the airport with government troopers conducting patrols, especially in "critical areas."
Manda said Tourism Secretary Richard Gordon has welcomed the double red alert.
For her part, Immigration Commissioner Andrea Domingo ordered all immigration intelligence agents posted at NAIA to closely screen and monitor arriving passengers, especially from Muslim nations.
Domingo also ordered foreigners from such countries to be placed under strict primary inspection to determine their purpose in coming to the country.
The BID had earlier noted that several foreign nationals with tourist visas identified Mindanao as their common destination, bolstering suspicion that suspected Abu Sayyaf sympathizers are coming to the country to support the bandit group.