A police officer has been stabbed in the back at Sydney’s Central Station.

The 25-year-old was taken to hospital after being attacked on one of the station’s platforms about 7:00pm on Saturday.

NSW Police said a man had been arrested.

A witness said there was blood on the ground beside a man who was seen being carried out by half a dozen officers, and there was pepper spray in the air.

A NSW Ambulance spokesman said three crews attended.

“We treated a 25-year-old man for a single stab wound to his back,” he told the ABC.

“He’s stable and has been taken to Royal Prince Alfred.”

A Sydney Trains employee who witnessed part of the incident said the arrested man was shot with a Taser.

“I just saw this Caucasian guy wielding a knife and the cops were trying to pacify him but he wouldn’t stop,” the man, who declined to give his name, told the ABC.

“He was shouting at the cops and then he didn’t stop so he was tasered.

A cop went down to platform one and grabbed the knife.”

The employee said the officers handled the situation “professionally”.