Man arrested after three bodies found in Sydney

A man is under arrest in hospital awaiting charges for the alleged murder of three people, including a child, found at two crime scenes.

The bodies of a seven-year-old child and a 41-year-old woman were found in a taekwondo studio in North Parramatta on Tuesday afternoon.

A 39-year-old man's body was earlier found with stab wounds at nearby Baulkham Hills after a concern for welfare report.

A 49-year-old man was arrested on Tuesday night after presenting to Westmead Hospital with apparent stab wounds and slash wounds.

Police will allege he killed the three people, Homicide Detective Superintendent Danny Doherty said on Wednesday, stabbing the man after earlier assaulting the woman and the child with "murderous intent".

"From the information we've received to date, we believe there's enough evidence to place them under arrest and have charges pending for murder," he said.

Det Supt Doherty sought further assistance from the public and encouraged anyone in the vicinity of the taekwondo studio on Monday night who may have seen or heard something to contact investigators.

Media reports suggest the crimes relate to a love triangle.