A Facebook post claimed the attacker “sprayed aerosol in the boys face before setting it on fire”.
Essex Police is now appealing for witnesses, with the atatcker described as wearing a black jacket, baggy black tracksuit trousers and white trainers, while hiding his face with a bandana.
Community leaders also raised serious concerns following the attack on the youngster on Saturday.
Steven Wakefield, Independent councillor for Shoebury, said: “This would have been a very scary incident for this boy.
“It is disgusting that this has happened and we do not want out town to become somewhere where you cannot go out.
“We should be able to enjoy our parks and walk around safely and it’s disgusting that someone would attack someone else in this manner.
“People must come forward with any information and they must not be frightened to do so.
“I hope the victim is doing ok now.”
The councillor insisted the area is safe despite the incident, and urged people to continue going out.
A spokesman for Essex Police said: “We are investigating after a 13 year-old boy was assaulted in Shoebury. It was reported the victim had been approached by another boy on a bike who had used a lighter and an aerosol can to create a flame.
“Nothing was taken but the victim’s hair was burnt. The other boy has been described as having a bandanna around his face and wearing a black puffa-style jacket with the hood up, baggy black tracksuit trousers, and white trainers.
“If you have any information you can submit a report online at https://www.essex.police.uk or use the ‘Live Chat’ button to speak to an online operator between 7am-11pm.
“Please quote the crime reference number 42/123814/21.
“You can also call us on 101 or contact Crimestoppers anonymously on 0800 555 111.”