A hero dog prevented a teenage gang fight from erupting by chasing them away.

The youngsters riding motorbikes had an argument at an intersection in Rayong province on Sunday night (December 6).

One of the riders and his pillion passenger were about to make a turn when a group yelled at them to stop.

They parked to talk and the aggressive bully tried to pick a fight accusing the pair of giving them a dirty look.

Soon after, another rider with a pillion arrived to back the bully and instigated the brawl by throwing a punch.

When things were about to become violent, the heroic Rottweiler, Lang-an, interfered with the fight.

CCTV footage shows Lang-an threatening the bully by barking before biting him in the buttocks.

The dog was patiently watching the unruly teens from the side of the road near its owner's store and struck after the first punch.

Lang-an chased away the bully and sent everyone running in different directions to save the two teens in trouble.

Benjarat Sangsiwarit, proud owner of Lang-an said, “He is a justice dog and doesn’t like it when someone is being hurt."

The woman came out of her store after the teens shouted for help and told everyone that they should check the security cameras installed nearby.

The teens escaped after knowing that there was police nearby so Benjarat watched the footage to know what happened.

She added: "My dog is a good boy for helping those in need. I am proud of my pet. I hope those teens have learned their lesson."