A 32-year-old man who shot a fellow passenger in the head on a New York subway train will not be charged because he was acting in self-defence, prosecutors said.

Terrified New York City commuters were left trapped in a carriage as gunfire rang out when a fight got out of control on Thursday during rush hour.

The shooting occurred around 4.45pm, when a 32-year-old man was confronted by an “aggressive” 36-year-old named by local outlets as Dajuan Robinson.

The incident started as a verbal dispute between the passengers but escalated quickly into a fight as the train left Nostrand Avenue station in Brooklyn.