Victorian detectives from a specialist crime squad are investigating after nine young people were stabbed in Melbourne’s CBD.

Police were flagged down by a 19-year-old Dandenong North man who had walked to Southern Cross Station around 2.20am.

The man told police he had been at a party at a Spencer Street address when a fight broke out and he sustained several stab wounds to the upper body.

He was conveyed to hospital in a critical condition where he remains.

Detectives from the Gang Crime Squad were brought in after a number of other males sustained non-life-threatening stab wounds, including a 19-year-old Langwarrin man and a 20-year-old Berwick man.

They presented at a nearby hospital about 3.50am.

Police said two 17-year-old youths from Truganina and a 17-year-old from South Melbourne went to a hospital in Werribee with non-life-threatening stab wounds.

A further three victims , all aged 19 from Wollert, Truganina and Lalor went to a hospital in Fitzroy about 2.45am with non-life-threatening injuries.

The trio subsequently discharged themselves from hospital.

It is believed that all nine males sustained the injuries at the Spencer Street address.

Police and Major Crime Scene Investigators are continuing to examine the scene and are keen to speak to anyone who may have witnessed the incident.

One bystander told the Herald Sun newspaper he saw a large group of people congregating in the area before the alleged fight broke out.

“There were heaps, some girls, some guys,” he said.

“They were mostly young, maybe 19 or early twenties.

“I don’t know what happened but they looked to me like they were drunk.

“I’m really scared, I just live around corner. If it was among the people I saw, that’s going to be really bad.”

Victoria Police at the crime scene on Monday morning. Photo: AAP

A crime scene has set up on Spencer Street and all traffic between Little Bourke and Bourke streets is being diverted around the scene.

Meanwhile, the ABC reported a second incident in the CBD overnight, with police called to second fight on Collins Street about 3.45am.

Two eyewitnesses, Peter and James, told the ABC they were at a city club when they saw two groups yelling at each other.

“After the yelling, they moved down the road because security was there, so they got away from them,” Peter said.

“Then someone threw a punch … and a bunch of other guys came in and then they all started hitting each other and full on it went all the way down the road around the corner.”

“It was real brutal, it was lucky the police arrived when they did,” James said.

Victoria Police said two men aged 20 and 21 were taken to hospital with minor injuries.

Anyone with information about either incident is asked to contact Crime Stoppers on 1800 333 000.

-with AAP