Two men are in custody after a man was stabbed to death and another was fatally assaulted in separate attacks.
Homicide detectives arrested a 51-year-old man after two food delivery riders were stabbed in Melbourne's city centre on Friday night.
Police allege the two riders saw the 51-year-old tampering with their bikes on Frederick Way about 8.10pm on Friday.
When they confronted the unknown man, a fight broke out.
Emergency services were called to the scene where one of the riders was found with serious stab wounds.
CPR was performed but the man, who has yet to be identified, was declared dead about 10 minutes later.
The second rider was located nearby a short time later and had also sustained an alleged stab wound.
Police said the 34-year-old was taken to hospital with non-life-threatening injuries.
The 51-year-old man was arrested in Footscray on Saturday and remains in custody.
In NSW, police are investigating the death of a man in Goulburn, in the Southern Highlands, after an alleged altercation on Friday night.
Emergency services were called to a hotel room on Bradley St shortly before 6pm after reports of a fight between two men.
Police and paramedics performed CPR on a 56-year-old man found unresponsive but he could not be revived.
A 39-year-old man was arrested before being taken to hospital with a head laceration.
After receiving treatment, the man was charged with common assault and granted conditional bail to appear before Goulburn Local Court on December 16.
Meanwhile, detectives continue to investigate another serious stabbing in Victoria on Friday.
Three people were taken to hospital with stab wounds, one with life-threatening injuries, after emergency services attended a house on Woodlee St in Dandenong about 11.30am.
Family violence detectives are investigating the circumstances surrounding the incident, police said.
