Four people were threatened with a knife during a home invasion in their Hunter Street house in Strathfield on Sunday night.
Three men walked in through an open door about 10.35am and demanded the four people at home hand over their belongings.
One man was armed with a metal pole, which he used to bash a 20-year-old householder several times, police allege.
Another man threatened the foursome - a 19-year-old woman and three men aged 19, 20 and 27 - with a kitchen knife.
They handed over a few items and the men stole a few other things from the house before leaving.
Police arrived a short time later and secured the crime scene.
Officers are seeking three men to help with their inquiries. One is of Pacific Islander or Maori appearance, in his early 20s, about 185cm tall, with dark tracksuit pants.
The second man looked Caucasian, in his late teens or early 20s, with a thin build, about 170cm tall, reddish-brown hair and a red hooded jumper and dark tracksuit pants.
The third man was described as looking Middle Eastern or Mediterranean, in his early 20s, about 170cm tall, with dark tracksuit pants.
Anyone who saw the incident or has any information should call CrimeStoppers on 1800 333 000.