One person has been killed on a central Melbourne street where a knife wielding man was left in a critical condition after being shot by police.
Two other people have been injured amid reports of a shooting and stabbing in Bourke Street on Friday afternoon.
Photographs from Bourke Street show a white sheet covering a body.
Footage from the scene show a man making stabbing gestures at two uniformed officers near a burning car before he was shot.
He has been taken to hospital in a critical condition under police guard.
One witness said a man was stabbed in the face.
Ambulance Victoria confirmed three people were injured.
"One person has been taken to hospital with a neck injury. They are in a suspected critical condition," they said.
"A second person has been taken to hospital with a head injury. A third person has also been taken to hospital."
Police initially responded to reports of a car on fire at the corner of Bourke and Swanston streets. The car was quickly extinguished.
Markel Villasin, 22, was finishing his shift at KFC on Bourke St as the drama unfolded.
"Me and the managers ran out and that's when we saw the car on fire and then we saw the guy on the floor and we wanted to help, there were two blokes helping him out already, he was face down pools of blood around his face," he told AAP.
"I'm pretty sure he got stabbed in the face.
"I really wanted to help but I was in shock, I didn't know what to do.
"Because he was on his stomach, they turned him over to see if he's alright, he was still alive."
Bystander Drew Hair told AAP he was walking on Swanston Street when he heard an explosion.
The next thing he saw was a "big dude punching into the police car".
Mr Hair said the assailant was dressed in Islamic clothing and of African appearance and about six foot four inches tall.
"The cops were trying to hit him with batons and he wasn't going down," he said.
Mr Hair said two civilians became involved as well as two police, trying to stop the man from his attack.
Witness Fiona told 3AW her friends had seen someone with a knife in the area and she'd been told he'd stabbed a security guard.
Another witness on a passing tram told ABC Radio it seemed police had been trying to subdue a man who was waving something.
"People around me screamed that he had a knife but I couldn't see clearly from where I was," Meegan May said.
"Then I heard a loud bang and someone said they could see someone doing chest compressions on someone as an ambulance started coming up the street as well."
The area is cordoned off and people are asked to avoid the area.
Australian Associated Press