This is the awful moment a bull terrier mauls a 10-year-old boy in just 30 seconds as he rides a scooter with his friends.

The powerful dog appears from nowhere before circling the small group several times, scratching the boys and turning on Callum Robins in the industrial city of Whyalla, north-west of Adelaide.

'It pushed me over then it attacked me pretty much,' Callum told Ten Eyewitness News on Monday.

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Callum Robins was left with deep bite wounds to his leg, arms and chest during the dog attack

The bull terrier's owner has defended the savage attack on Callum Robins, 10, as a 'playful bite'

The savage attack left Callum with deep and long bite wounds to his leg, arms and chest as he was pinned to the ground.

A hero's quick action in pulling the dog off the boy prevented an even worse tragedy.

The boy's mother Kassy Myers said she found her son's wounds, requiring three operations and plastic surgery, rather confronting.

'I felt sick to my stomach,' she said. 'If that can happen in 30 seconds, God knows what can happen in a minute.'

The attack left Callum Robins with long bite wounds requiring three operations to fix

The dog's owner has defended the attack as a 'playful bite', Ten Eyewitness News said.

However Callum's family want the bull terrier put down.

'I don't think a dog that is that aggressive should be out on the streets, especially when the children didn't do anything to antagonise the dog,' Ms Myers said.