Boy, 6, 'slashed while trying to stop father attacking mother' in Sydney

A six-year-old boy was allegedly slashed while trying to stop his father from stabbing his mother in western Sydney.

Police have been told the boy and a 27-year-old woman were stabbed inside a North Parramatta unit before a man fled.

Emergency workers were called to the apartment just after midnight on Saturday.

The boy ran into the street, screaming for someone to call Triple Zero. PolAir and the dog squad launched a search for the man.

"It's atrocious that happens in a home with a young child present," NSW Police Assistant Commissioner Karen Webb said.

A 31-year-old man was arrested about 2am after he turned up at Parramatta Police Station and police said their inquiries were continuing.

The accused was undergoing a mental health assessment at Blacktown Hospital, when he complained of having a sore throat.

He's since been tested for coronavirus, delaying his police interview for up to 24 hours.

Neighbours told 9News the boy's bravery was astounding and they're sure he saved his mother's life.

The woman and boy were taken to hospital in a stable condition.