A man was assaulted outside the Belly Busters kebab shop on Lynchford Road around 7 p.m. on Sunday, July 3.
An altercation broke out inside the shop, spilling out onto the street.
A man was later discovered unconscious on the ground.
Officers have been conducting investigations but are now seeking public assistance.
Police believe there were several people inside the shop and are appealing to them for information.
Were you in the neighbourhood at the time? Were you present when the incident occurred?
Do you have any dashcam or CCTV footage that could aid the investigation?
Anyone with information should call 101 and reference 44220265399. Alternatively, you can submit information online at https://www.hampshire.police.uk/tua/tell-us-about/cor/tell-us-about-existing-case-report.
You can also contact the independent charity Crimestoppers completely anonymously at 0800 555 111 or through their anonymous online form at crimestoppers-uk.org.