Police said the trio approached a home on Allison Drive in Girrawheen last night and introduced themselves as police officers.
The men allegedly produced a badge before they were let inside by a 76-year-old male resident.
After gaining entry, the offenders allegedly bound the 76-year-old and assaulted his 73-year-old partner who was in another room.
Detective Inspector Gary Butler said the men stole jewellery of “extremely large value” before fleeing on foot.
“Violence of this nature is unacceptable and it will not be tolerated,” he told reporters today.
“The community deserves the right to feel safe and secure in their homes, the public should feel outrage.”
Butler said some stolen items have been recovered and urged anyone with CCTV or information about the attack to contact police.
He described the offenders as having olive complexions and wearing dark-coloured long pants, shirts and long-sleeve jackets.
Two of the men are about 165cm tall and the third is described as being between 185cm to 190cm tall.
“We will not stop until these offenders are apprehended and placed before the courts,” he said.
Butler said the incident was “unusual” and that plain-clothes police officers would never attend a home without proper identification.
“We would like to remind the public all plain clothes officers must show photographic identification,” he said.
The couple were taken to hospital with facial bruising and contusions.
The 76-year-old man has returned home and is receiving support from family.
Butler said the 73-year-old woman is continuing treatment at hospital.
“She’s traumatised and very sore,” he said.
