Police are investigating two incidents that occurred in Werribee on Saturday night (31 Oct).
During the first incident, a brawl involving about 20 youths occurred in parklands on Rosella Avenue shortly before 7pm. Witnesses say the youths were walking through the streets with large knives.
A male teenager was taken to hospital with a non-life threatening leg injury.
Police are also investigating an attempted robbery about an hour later.
Two male teenagers were walking along Heaths Road when they were approached by five males wearing balaclavas.
The offenders demanded the victims hand over their mobile phones, which their refused and walked off.
One of the offenders then struck one of the victims in the back of the head with a machete.
He contacted his mother to pick him up and was taken to hospital with non-life threatening head injuries.
Police are investigating whether the two incidents are linked.
Any witnesses or anyone with information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online atwww.crimestoppersvic.com.au