At about 4.30pm, two men got out of a taxi on New Bedford Road, near the junction of Austin Road.
They assaulted the victim and threatened him and his friends with a knife while racially abusing him.
Both offenders were described as white, aged between 25 and 35.
One offenders was described as medium build with ginger hair, facial hair and wearing a black sports top with a white stripe down the sleeves.
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The second offender is described as having a red beard which was short on the sides and long at his chin. He was wearing a black cap and black clothing.
Hate Crime Sergeant James Hart said: “This was an unprovoked attack, the boy and his friends were going about their business when they were attacked by the offenders, who also made racist comments.
“It is being treated as a hate crime, which we take very seriously. Hate crimes are based on ignorance, prejudice, discrimination and have no place in our society.
“The victim suffered bruising and was very shaken by the incident. It was a busy road and we are appealing for anyone who may have seen or heard anything to come forward.”
Anyone with information should call 101 quoting reference C/40138/2017.