MANILA - The Manila International Airport Authority (MIAA) on Friday advised passengers with flights scheduled to depart from the Ninoy Aquino International Airport (NAIA) to arrive at the terminals early to avoid delays amid heightened security measures.

This amid heightened security in the wake of the attack at Resorts World Manila before dawn Friday, where 37, including the still unidentified gunman, were killed.

• TIMELINE: Resorts World Manila attack

The incident had prompted airport authorities to shut down operations at the airport from 1:45 a.m. to 3:45 a.m. given the casino's proximity to the complex.

The MIAA said the Office of Transportation Security placed the airport complex at "Security Condition 3" as a "deterrent action against attempts to disrupt peace and order in the airports."

The security level means "specific protective measures are maintained for a limited time when a security incident is imminent or probable."

MIAA security is meanwhile "on high alert status," the agency said in a statement.

Under the airport's heightened alert, more security officials armed with long firearms were deployed to "conduct rigid vehicle inspections" and "deter action against attempts to disrupt peace."

The airport will also enforce heightened screening measures at its terminals.

"Passengers are therefore advised to be at the airport early and have their identification and travel documents ready and in order," said the MIAA.

The airport authority also suspended the issuance of special access passes for non-passengers "except for purposes of reporting for work, transacting official business or [requests that are] diplomatic in nature."

MIAA General Manager Ed Monreal said the measures "are not meant to sow fear, cause alarm, or even scare the public... [but are] called for so airport users can be assured of a safer airport environment."

He said no flights were canceled or diverted during the two-hour NAIA closure.