Police are appealing for witnesses after two teenagers were assaulted on a bus.

The assault happened on the 359 bus which travels from Bristol to Portishead and left Bristol at 11.30pm on Friday September 23, 2011. Two young men, aged 17 and 16, were on the bus and were in an argument with two or three men.

At around 12.05am the bus stopped at the junction of the Portbury Hundred and Sheepway in Portishead. Two men grabbed one victim by the throat and pushed the other in the chest.

An investigation has begun and police enquiries are underway to identify the people responsible. 

One suspect is described as a white man, 6'2" tall, around 60-years-old and with a white/grey beard. He was wearing a burgundy jumper.

The second suspect is described as a white man, 5'11" tall with a proportionate build and short, grey hair. 

Investigating the incident, PC Dave Lovell said: "There were several other people on the bus who may have seen what happened and I would ask those people to get in touch with us. It is believed that one of the other passengers may have known of one of the suspects and to that person I would say please get in touch with us or pass on what you know through Crimestoppers."

Anyone with information should contact Avon and Somerset Police on the non-emergency number 101. Alternatively, phone the independent charity Crimestoppers on 0800 555111. They never ask your name or trace your call.