The 19-year-old lifeguard was on patrol at Casey ARC in Narre Warren when he was approached by a group of youths and assaulted just before 6pm, police said.

9News understands the group were earlier spoken to by the same lifeguard for performing dangerous stunts, such as flips, close to other swimmers.

The lifeguard was headbutted, kicked and punched by the group.

He was taken to Dandenong hospital with bruises, cuts and scratches across his upper body and has since been discharged.

The group of youths fled the scene on Overland Drive and remain on the run.

City of Casey Mayor Stefan Koomen said the council had taken “immediate steps to increase security” at council-owned aquatic centres.

“On behalf of the council, I want to reassure our community that we are deeply committed to making our aquatic facilities safe for everyone to enjoy,” Koomen said.

“We are actively supporting the police investigation and providing all necessary assistance.

“We are taking immediate steps to increase security at all our aquatic centres to ensure a safe environment for everyone.”

Anyone with information can contact Crime Stoppers on 1800 333 000.