SYDNEY - A teenager who shot to worldwide fame after throwing an egg at a far-right Australian senator days after the Christchurch terror attack was handled an official caution by the Australian police.

"The 17-year-old boy has been issued with an official caution in relation to the incident," Sydney Morning Herald (SMH) quoted a Victoria Police spokesman as saying.

The boy, identified as Will Connolly but later gained the nickname Egg Boy, smashed an egg on the head of anti-immigration Australian senator Fraser Anning while he was speaking to reporters last month.

The footage, shared widely on social media, showed Mr Anning being approached from behind at a political event, before having an egg cracked on the back of his head.

The incident happened after Mr Anning was widely condemned for a statement he made that day blaming the March 15 massacre in Christchurch, New Zealand, on Muslim immigration.

The footage showed Mr Anning appearing to try to hit Mr Connolly, before the teenager was dragged to the ground.

Mr Connolly was also assaulted by an unknown man.

Video of the incident went viral, with people around the world rallied around "Egg Boy" as a hero and symbol in the fight against bigotry.

According to SMH, Mr Anning was not charged for his remarks.

"A decision has been made not to charge the 69-year-old man," the police spokesman said "On assessment of all the circumstances, the 69-year-old's actions were treated as self-defence and there was no reasonable prospect of conviction."

However, the police is looking for a man they believed assaulted Mr Connolly.

"While the 17-year-old boy was being held on the ground, another male has approached and kicked him in the body a number of times," SMH quoted a police spokeswoman as saying on Monday.