Sydney man shot by police at Campbelltown Train Station undergoing emergency surgery

A man who was shot by police officers after allegedly threatening them with a knife at a Sydney train station is tonight undergoing emergency surgery.

9News understands the man, aged in his 30s or 40s, suffered a stomach wound after he allegedly lunged at police with a 30-centimetre knife about 3.45pm today.

Officers from the Police Transport Command were speaking with the man near Campbelltown Railway Station after he allegedly tried entering without a valid ticket, before an altercation occurred.

The man allegedly challenged police with the knife on Hurley Street, just outside the station, and police deployed a taser that was unable to stop him from continuing to threaten officers.

“He again confronted the police with a knife, which has been described to me as about 30cm long, aggressively confronted the police and a single shot was fired into this male," NSW Police assistant commissioner Peter Thurtell told reporters this afternoon.

“It is concerning that anybody would carry a knife in public. Policing is a dangerous job, we all know that.”

The man was rushed to Liverpool Hospital following the incident and is undergoing emergency surgery, but is expected to survive.

Authorities also have little information about the man, who was not carrying identification at the time of the incident.

No-one else was injured in the altercation.

Bus services in the area were temporarily affected by the altercation, forced to drop commuters off at another location, while trains rain as normal.

“Cars backed up, there were so many police and they were circling for ages after the actual incident happened," one witness told 9News.

A crime scene has been established at the train station, which is expected to remain tonight, and police have asked people to avoid the area as the investigation continues.

A critical incident investigation has also been launched, while the officer who shot the man is being supported by counsellors.

Police are not searching for anyone else in relation to the incident.