The man was again refused bail and his case adjourned for mention at Moree Local Court until Monday, September 13, where he will appear via audio-visual link.

Homicide squad detectives arrested the Narrabri man on Tuesday afternoon in the regional town, just days after the child was hospitalised with serious head injuries.

The child was flown to The Children’s Hospital at Westmead on Sunday and died the following day.

The 21-year-old man was charged with murder and two counts of aggravated sexual assault of a child under 10.

The homicide squad, with the assistance of local detectives, launched Strike Force Woore to investigate the child's death. Strike Force Woore comprises detectives from the State Crime Command’s Homicide Squad and Barwon Local Area Command, with assistance from specialist police. Police would not comment on the case, but the Department of Community Services has confirmed a second child was removed from the house and is in the care of a family member.