There were no immediate reports of injuries.

Video shared on social media and verified by AFP showed multiple vehicles ablaze in a car park in terminal three.

The heat index is expected to reach 41°C at the airport today, according to the state weather forecaster.

“It started with one car that caught fire in the car park then the rest of the vehicles followed because it was so hot,” said Lane Macleod, who filmed one of the videos from inside the terminal.

“We were inside the airport at the time. We just saw it from the window,” she told AFP.

Flight operations were unaffected by the blaze, the Manila International Airport Authority (MIAA) said in a statement.

The MIAA said it received a report of the blaze at around 1.30pm local time and the fire was extinguished within half an hour.

Fire officer Kristine Germino said it was not known what caused the grass fire.

The months of March, April and May are typically the hottest and driest in the archipelago nation but conditions have been exacerbated by the El Nino weather phenomenon.

The country’s heat index measures what a temperature feels like, taking into account humidity.

The actual temperature in the capital reached nearly 37°C by mid-afternoon.