MANILA - The Philippines has placed 42 commercial airports across the country on heightened alert on Friday as authorities validate bomb threats sent via email, the Civil Aviation Authority of the Philippines (CAAP) said.

"All 42 CAAP commercial airports are on heightened alert as of today, Oct 6, following a warning received by the Air Traffic Service via email that aircraft from Manila, bound to Puerto Princesa, Mactan-Cebu, Bicol, and Davao International Airports are about to be set off by a bomb," the CAAP said in a statement.

"While the information is currently under validation, immediate enhanced security measures are being implemented across all airports," CAAP said. "All CAAP airports and area centers shall augment adequate security personnel to manage the expected high volume of passengers and vehicle traffic," it added.

On Oct 4, Ricardo Banayat of the CAAP Security and Intelligence Service issued a memorandum instructing officials "to augment adequate security personnel" in the wake of the threats.

In a separate statement, Transport Secretary Jaime Bautista said patrols and K9 units had been deployed at all terminals as an added precaution. "There are no expected impacts to any scheduled flights and we would like to ensure the traveling public that protocols are in place to ensure everyone's safety and security," he added.

According to Bautista, the Manila International Airport Authority is closely coordinating with the airport police and other law enforcement agencies to validate the threat.

Authorities advise passengers to brace for intensified security inspections at the airports.