Police are appealing for public assistance after a man was assaulted on a bus in Sydney this afternoon.

Shortly after 3pm a bus travelling from Sydney’s Northern Beaches entered York Street in Sydney’s CBD when an altercation occurred between a man and a group of youths.

As a result one of the youths allegedly produced an object and struck the 40-year-old man on the head.

The male and his friends then fled the bus on foot.

The injured man sustained a head injury and was taken by ambulance to Sydney Hospital in a stable condition.

A crime scene has been established and inquiries into the incident are continuing.

Police wish to speak to a male described as Caucasian in appearance, aged 15-16 years