The victim was waiting for a bus on Thursday on St Clements Street, Oxford, when a car pulled up next to him.
He was approached by the front-seat passenger before running on to Rectory Road where he was followed and attacked, police said.
There were up to six offenders thought to be aged between 18 and 20.
The boy is currently in hospital and officers are appealing for witnesses to what they have described as "an isolated incident".
The front-seat passenger of the dark people carrier - possibly a Volkswagen Touran - is described as Asian, about 6ft 3ins, of a slim build and with short black hair.
He was wearing a grey tracksuit with elasticised ankles and a grey tracksuit top which had darker grey arms.
A 16-year-old boy suffered a fractured skull when he was attacked by a group of men, including one wielding a hammer.