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

According to the police, 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 licence plate and fled the scene.

Superintendent Lam Kai-chor said while they are still investigating a motive for the attack and whether it's related to the victim's job, no evidence showed 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."

Lam did not rule out the possibility of further arrests.