Manhunt under way after Sydney police woman shot

The police dog squad has joined the search for a man who shot a police officer earlier this morning in Sydney's south-west.

Constable Elizabeth Roth, 34, was alone at Wetherill Park police station when a man came in looking to speak to detectives.

He waited almost two hours and then, just after 6:00am local time, allegedly jumped the counter and shot the constable in the lower chest with her own weapon.

Police Commissioner Ken Moroney says the officer is a serious but stable condition and is expected to make a full recovery.

"The bullet appears to have travelled across the face of her lower abdomen, fragments of the bullet have hit her," he said.

"We've recovered some of those fragments, but the other fragments will need to be removed by surgery later today.

"There is an intense forensic investigations going on of the crime scene, to not only pick up issues of DNA, but indeed, the other part of the bullet."

He says police believe they know the identity of the offender, who is described as of Asian appearance with long, black hair.

It is understood he is still armed.

- RADIO AUSTRALIA