Wayward Taskforce detectives are investigating after a boy was robbed and assaulted in Williamstown last week.
The 13-year-old was walking along Electra Street when he was approached by four male youths about 5pm on Saturday, 3 October.
The teens assaulted the victim and pushed him against a fence before stealing his phone and fleeing.
The offenders were later seen walking along Ferguson Street, Williamstown a short time later.
The victim was not physically injured during the incident.