A man is in custody after two female police officers were allegedly physically assaulted while attending a welfare check in Sydney.

The two officers were called to Bunya Road in Bidwill, near Mt Druitt, after reports of a man lying on the road at 6.30pm yesterday.

The officers, aged 23 and 22, tried to talk to the man when he allegedly became aggressive and kicked the 23-year-old in the stomach before hitting her in the head.

She fell unresponsive while her 22-year-old partner tried to intervene, but is understood she was also assaulted.

She tried to use capsicum spray on the offender when two other officers arrived on the scene, and they were able to subdue the 19-year-old man.

The 23-year-old officer was treated by paramedics at the scene and was taken to the hospital in a stable condition.

She has since been released from care after being treated for a concussion.

The second officer was taken to hospital as a precaution and was treated for bruising and scratching.

The 19-year-old man was taken to the police station and then to hospital for a mental health assessment.

Charges are expected to be filed today.