Queensland police are investigating an alleged assault that left a 66-year-old security guard with a serious head injury at a shopping centre in Coomera on September 22.

Police said the guard approached a group of young people at the Foxwell Road shopping centre at about 6:40 p.m. Two young males allegedly assaulted him, causing him to fall to the ground.

The man was taken to Gold Coast University Hospital in serious condition. Investigators are appealing for witnesses, information or relevant vision that may assist the investigation.

Information can be provided to Policelink through the Queensland Police online reporting system. Anonymous reports can be made to Crime Stoppers on 1800 333 000. The police reference number is QP2601880243.