Police have arrested eight men reportedly with a triad background, after a prison officer was attacked outside Pik Uk prison in Sai Kung yesterday.

Three masked men equipped with "long hard objects" attacked the corrections officer when he was waiting for a bus near the prison at about 12:50pm.

The trio, aged 16 to 37, then got in a private car with a fake license plate and fled the scene.

Superintendent Lam Kai-chor said while they are still investigating a motive for the attack, whether it's related to the victim's job, no evidence shows correlation to the victim's financial situation or personal life.

"There are a total of six cuts that are five to 10 centimetres long on the victim's head and upper limbs, and a fracture on his right wrist. The victim is now stable and remains in hospital for treatment," he said.

"Also, during the chaos, the three men hit a 33-year-old woman and her two-year-old daughter. They sustained minor injuries and left the hospital after treatment without any issues."

He did not rule out the possibility of further arrests.