Watch dramatic footage of the moment an alert police officer tugs a man back from the brink of almost certain death under a train.

A quick-thinking police officer has averted a tragedy when he grabbed the shirt of a man who appeared to be about to leap into the path of an oncoming train in Colombia.

The drama was caught on camera at Hospital station in the city of Medellin.

The video first shows the man acting unusually on a platform as the train approached the station.

As he suddenly lunged towards the train as it arrived, the officer grasped him and dragged him back onto the platform.

Unconfirmed reports have suggested the heroic policeman is Gustavo Charrapo.

Responding to a YouTube post of the video, he said: "Thanks to everyone I want to give recognition but it is my job to protect and serve the community! and will continue to do!"

Clicky for video.