Man wearing 'Keep Calm' shirt in bloody fight at NFL training

WARNING: Graphic Content

A bloody fight has erupted at an NFL pre-season scrimmage between two Tennessee Titans fans arguing over a mobile phone.

One man, ironically wearing a 'Keep Calm' shirt, reportedly took a phone from the possession of a man wearing a Batman shirt, and refused to immediately give it back.

In retaliation, the man wearing the Batman shirt punched the fellow Titans fan in the face, sending blood pouring out of his mouth.

An ugly scuffle ensued, in which the 'Keep Calm' man gets 'Batman' in a headlock where a number of fairly ineffective jabs were thrown.

A third Titans fan eventually broke the warring pair up.

The first punch is thrown. Pic: Twitter

After retrieving his phone, the bearded 'Batman' shirt assailant attempted to flee the scene, but was quickly grabbed by security to the cheers of the crowd.

Police were not involved in the incident.

The scuffle continues. Pic: Twitter

Remarkably it's only one of a number of violent incidents at NFL games in recent times, often between fans of the same teams.

In this instance, Oakland Raiders fans turned on each other in one of the most bizarre fights you'll ever see.

Earlier in 2016, Rams and Chiefs fans turned on each other during a pre-season game.

There have also been a number of incidents involving violence against officials at gridiron games in recent years.