Man allegedly assaulted, woman and infant avoid injury after home invasion in Sydney's south-west

An 18-year-old man has been assaulted during an alleged home invasion in Sydney's south-west overnight, but two other occupants of the property have avoided injury.

Police said three men allegedly forced entry into the home on Lintina Street in Tahmoor before assaulting the man.

Officers believe "shots were fired" at the time, but there were no reports of gunshot wounds.

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The trio fled the home on foot, shortly before police arrived at the scene about 10.40pm.

The 18-year-old was treated at the scene by paramedics and taken to Campbelltown Hospital in a stable condition.

Two other occupants of the home, an 18-year-old woman and an infant child, were not injured.

Police have established a crime scene and investigations are continuing into the incident.