A man performed a sex actupon himself before assaulting a 13-year-old boy.
It happened on a bus travelling from Rochdale Bus Station to Middleton at about 11.30am on 21 April 2015.
Police have now issued a CCTV still of a man they want to speak to in connection with the incidentand are appealing to anyone who recognises him to come forward.
The 13-year-old was sat onthe upper deck of the bus, towards the back, when it left Rochdale Bus Station.
About 15 minutes later, the offender got on and sat near to the young boy. He then performed a sex act upon himself.
Minutes later, the offender then moved in order to sit closer to the young boy, and then sexually assaulted him.
The offender then left thebus close to the Hopwood Hall College area of Middleton.
Police have now issued a CCTV image taken from the bus of a man they wish to speak to in connectionwith the offence and are urging anyone with information to come forward.
Police Constable Steve Farnellsaid: “This young boy was absolutely shocked to see the offender performing a sex act in such close proximity to him, but became even more distressedwhen the offender sat next to him and physically assaulted him with a clear sexual intent.
“No-one, not least someone of such a young age, should ever be subjected to this sort of sexual assaultand we need to find this man as clearly he is danger to other people.
“Most buses and public transport are equipped with CCTV these days so we have been able to issue a quite clear still of the man we wish to speak to in connection with this offence.
“I would ask people to look carefully at this image and urge anyone who has information or who recognises the man in this picture to call us as soon as possible.”
Anyone with information is asked to call police on 101 or the independent charity Crimestoppers, anonymously,on 0800 555 111.