Sydney martial arts instructor arrested for alleged murder of South Korean family

A Sydney martial arts instructor has been arrested for the alleged triple murder of a South Korean family living in the city after a child and woman were found dead in a Taekwondo centre, Australian police said on Wednesday.

Police arrested the 49-year-old man in hospital late on Tuesday night, Detective Superintendent Daniel Doherty told a press conference.

The man, who is under police guard and expected to be charged with three murders, was being treated for apparent stab wounds to his chest, arms and stomach, according to a separate police statement.

Police said he arrived at Westmead Hospital in Sydney's northwest just before midnight on Monday and subsequently told officers he had been attacked in the car park of a supermarket.

In the course of investigating the man's assault on Tuesday morning, police found the body of a 39-year-old man in the suburb of Baulkham Hills in the city's northwest with what appeared to be multiple fatal stab wounds.

Two hours later, police found the bodies of a 41-year-old woman and seven-year-old boy at a martial arts centre in the nearby suburb of North Parramatta.

Police believe the family of three were originally from South Korea and lived in Baulkham Hills. Police have contacted the country's local consulate.

"They (the woman and child) were subjected to an assault, we'll allege it was with murderous intent and they died from their injuries," Doherty said.

Doherty said the seven-year-old regularly took Taekwondo lessons in the centre where his body was found and knew the instructor. He had been set to attend a session on Monday, the day he was allegedly killed.

Police said it was too early in the investigation to speak about motive.