Police officer allegedly stabbed in head in Sydney

Two police constables were on traffic duties when the 33-year-old allegedly approached and stabbed the male officer with a 30-centimetre kitchen-style knife on the corner of Castlereagh Street and Park Street in Sydney's CBD.

The officers, including the one allegedly stabbed in the head, chased the man.

He was eventually tasered by riot police and arrested.

The alleged offender has been arrested and taken to Royal Prince Alfred Hospital for assessment under police guard.

NSW ambulance paramedics treated the officer for non-life-threatening head injuries before he was taken to St Vincent's Hospital.

The police officer, who works at the King Cross station, was "doing fine" and has lots of support around him, Detective Superintendent Martin Fileman said.

Police said there was no ongoing threat to the public and while the man was known to police, it was not for any significant matters.

Police should have more power to search people for knives, the detective superintendent said.

"I think it just shows you the risk that knives pose in the community," he said.

"[It] just shows you the serious risks that people carrying knives pose to the community. But we do train for these incidents, and we train very hard for these incidents."

About a month ago, Joel Cauchi killed six people in at Sydney's Bondi Junction Westfield with a knife.