Police have released CCTV images of four men they are keen to trace in connection with a large fight in Leeds city centre.
A 24-year-old man received a serious head injury during the incident.
The suspects, who are believed to be Portuguese, were involved in the attack at Millennium Square at around 4am on Saturday, April 16.
It is believed that the fight broke out after those involved left a nearby Indian restaurant after a birthday party.
Two men were arrested at the scene and were later released on police bail pending further enquiries.
Detective constable Rob Miller, of Leeds District CID, said: “This was a very serious incident and we are appealing for any information that could assist us in identifying the suspects.
“The CCTV images of them are fairly low quality but we feel the men will be recognisable to anyone who knows them from their clothing and general appearance.”
Anyone with information is urged to contact DC 6397 Miller at Elland Road via 101 or independent charity Crimestoppers anonymously on 0800 555 111.