A man has been charged with break-in offences after a Sydney police officer accidentally shot himself in the leg while making an arrest.

Police say the 31-year-old acting sergeant was reholstering his gun when it went off after he and three colleagues spotted an attempted break-in at the entrance to Westfield in Chatswood, just before 5.30am (AEDT) on Thursday.

The officers were on a routine patrol of the shopping district when they disturbed a man trying to break in to a number of shops on Anderson Street, Detective Inspective Peter Yeomans said.

"The officer drew his weapon in attempting to arrest the offender prior to the offender fleeing from the scene," he told reporters in Sydney.

"It appears at that stage that the officer has tried to reholster his weapon. It was ... an accidental shooting."

The officer, with seven years in the force, was rushed to Royal North Shore Hospital with a gunshot wound to his right leg.

He is in a stable condition, a hospital spokeswoman said.

Det Insp Yeomans said the acting sergeant, described as a respected member of the local community and Chatswood police station, would undergo an operation later on Thursday.

"He seems in good spirits at this stage," he said.

"He will be admitted and there will be surgery later this evening."

A critical investigation team is now investigating the shooting, with police cordoning off parts of Anderson St on Thursday morning.

A Surry Hills man has been charged with two counts of break, enter and steal, and two counts of attempted break, enter and steal.

He has been refused bail to appear at Hornsby Local Court later on Thursday.