The youths are reported to have had an altercation with a rough sleeper on Trinity Road on Sunday March 15, at around 9pm.
Det Sgt Amy Keane-Christie said: “If you witnessed an altercation between a man and a number of youths on Trinity Road then please come forward.
"You may have seen or heard something which is key to our investigation.
"It is also important for you to check your privately-owned CCTV or dash cam footage if you were driving in the area at that time, as this may have captured the incident.”
Anyone who can help should call police via 101, quoting log 597 of March 15.