A 19-year-old woman has been fatally assaulted in a short-stay apartment in Melbourne's CBD after a dispute between two groups of young people at a party.

Emergency services were called to the EQ Tower in A'Beckett Street, about 5:15am following reports of a woman suffering serious injuries.

Paramedics treated the woman but she died at the scene.

Victoria Police Commander of North West Metro region, Tim Hansen, said a group of young people rented a short-stay apartment on the 56th floor.

"During the course of the night a second group of young people have arrived there and a dispute of some nature has occurred, resulting in the victim… being assaulted," Commander Hansen said.

He declined to comment on reports the woman, who was from Pakenham in Melbourne's outer south-east, had been stabbed.

The dispute happened on the 56th floor of the building. ( Supplied: Booking.com )

Commander Hansen said the second group fled the building after the assault, leaving a "fairly chaotic scene".

"They certainly weren't there when we got there. There is CCTV available to us and we're reviewing that currently," he said.

He said it was unclear whether the second group had been invited to the apartment, but the incident did not appear to be a random attack.

"We're trying to clarify what brought them there," he said.

"There was some connection between these groups."

Homicide squad detectives have taken charge of the investigation and about 12 people were assisting police with their inquiries.

"We've put support around the family. We are reaching out not only to the family but also the extended community of the victim, and we're making sure that they're supported through this," Commander Hansen said.

He said police believed everyone at the apartment during the incident were in their late teens or early twenties and were of African-Australian heritage.

Commander Hansen said the victim was also of African-Australian heritage.

Anyone with information is urged to contact Crime Stoppers on 1800 333 000.