A police officer is in a stable condition after his gun went off during an arrest on Sydney's north shore this morning.

The incident happened just before 5.30am at a shopping centre on Anderson Street in Chatswood.

Police say it appears the officer's firearm discharged while he was making an arrest and that he received a gunshot wound to the leg.

He was treated at the scene by paramedics and taken to Royal North Shore Hospital in a stable condition.

Sergeant Dave Rose says it is still unclear how events unfolded.

"It's obviously very early stages for us and we're obviously still trying to determine exactly what has occurred," he said.

Police say the matter is now being examined by a critical incident investigation team.