Residents were baffled seeing a bizarre phenomenon that caused sky mixed between light and dark.

Footage shows the horizon appearing to be divided between night and day in Mandaue City, the Philippines on October 10.

One side was seemingly being illuminated by sunset rays while the other was already darker.

Onlooker Leylan Romarate said he recorded the scene without using a filter - which is supported by the video metadata.

He can be heard spin g in the video the video: 'There is a line right there. It is day time and evening. What is this? There is no filter on my phone camera.'

Speaking after, Leylan said it was the first time he had seen the sky like that.

He added: 'Many people saw this too, not just me. Is this something natural? I have never seen that happen before.'

The phenomenon where one part of the sky experiences daylight while the other part experiences night or twilight is caused by the 'terminator' or 'twilight zone.'

The terminator is the moving line separating a planet's illuminated or daylit side from its night side. This division happens due to the planet's rotation, creating a gradual transition between day and night known as the twilight zone.