Mill Park Divisional Response Unit are investigating three aggravated burglaries and an armed robbery at separate massage parlours throughout the northern suburbs from August to October.
It is believed an unknown man attended a massage parlour on Spring Street in Reservoir on Tuesday 27 August about 11.30pm.
The man entered the staff only area and stole mobile phones belonging to staff before fleeing the premises.
It is understood the same man attended another massage parlour on Tuscan Court in Thomastown on Wednesday 28 August about 2am.
Officers have been told the man engaged in services, which he then paid for with a mobile phone stolen from the incident on 27 August.
The man left the premises and returned at 2pm when he entered the staff area and stole a purse belonging to a staff member.
Weeks later, the same unknown man attended the same massage parlour on Tuscan Court on Tuesday, 17 September about 6.30pm.
The man entered the staff area and stole a purse belonging to a staff member before leaving the premises.
The following month, the unknown man re-attended a massage parlour on Tuscan Court on Saturday, 19 October about 2.45am.
It is understood the man approached a staff member and produced a knife, making demands for cash.
The man took an amount of cash and left the premises without physically injuring the staff member.
Investigators have released CCTV and images of a man who may be able to assist with their enquires.
Anyone who witnessed the incident or with information is urged to call Crime Stoppers on 1800 333 000 or log onto www.crimestoppersvic.com.au.
