A 25-year-old Thomastown man died after he was assaulted and stabbed at a home in Heidelberg West on October 16.
A 20-year-old man from Reservoir, who was allegedly kidnapped, was found inside a car left at the property.
Police believe up to 10 offenders were involved.
Nine people have been arrested, with four taken into custody at Melbourne Airport.
Four 17-year-olds and a 19-year-old from Preston have been charged with both murder and kidnapping, while two 18-year-olds and a 16-year old have been charged with kidnapping.
Another 16-year-old was arrested earlier in November but released pending further enquiries.
Detective Inspector Dean Thomas from Victoria Police's Homicide Squad said investigators would hold anyone involved to account.
"I know many will be horrified by the young age of those arrested but let me make this clear – we will be relentless in pursuing anyone responsible for this level of violence and age will be no barrier to that," he said in a statement.
"Carrying knives will result in tragic outcomes for all parties concerned and the ramifications are severe and life changing.
"A young man has senselessly lost his life, and a significant number of families now face a lifetime of grieving."
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