An assault in the foyer of Box Hill Hospital has left one employee, believed to be a surgeon, in a critical condition.
Eastern Health confirmed one of their staff members had been injured in the attack on Tuesday which they described as a "terrible incident".
Police confirmed an altercation occurred between two men at the hospital about 7.20pm.
"It's believed a man was walking into the Arnold Street premises when he became involved in an altercation with another male standing in the foyer," a Victoria Police spokeswoman said.
"The second man has then seriously physically assaulted the first man and left the scene."
A caller to radio station 3AW said the man injured in the attack was a surgeon at Box Hill Hospital who sustained serious head injuries after being king-hit and knocked to the ground.
The surgeon was reportedly concerned about people smoking near the doors of the hospital when he was assaulted.
An Eastern Health spokeswoman said they were working with police and that the man's family didn't want him identified.
"We can confirm that police are investigating the assault of a staff member at Box Hill Hospital last night. The staff member was stabilised before being transported to The Alfred in a critical condition."
"This is a terrible incident and we have been in contact with the staff member's family. They have requested privacy at this time."
Police are yet to arrest the person responsible for the assault and have released CCTV images of a man they wish to speak to.
The offender is described as Caucasian, aged between 20 and 30 years old, with a medium build.
He was wearing all-black clothing and a black cap at the time of the incident.
While the man's role at the hospital is unconfirmed, several surgeons and emergency physicians have expressed solicitude on social media in the wake of the assault.
"This is a tragedy," one man posted on Twitter.
"My fingers crossed and best wishes to the victim & all of my friends at Eastern Health."
Anyone with information can contact Crime Stoppers on 1800 333 000.