Paramedics transported a 17-year-old male to the Royal Melbourne Hospital about 6.45pm on Good Friday.

Ambulance Victoria spokesman John Mullen said the patient was transported in a stable condition.

Kyneton Sergeant Jan Stroek said the victim was returned to the youth justice centre about 4am on Saturday. 

He said three alleged offenders were isolated following the assault.

Police investigations are ongoing, a Victoria Police spokesman said.

Three police units from Kyneton and a detective from the Central Goldfields area attended the youth justice centre about 6.30pm on Good Friday. 

The assault has prompted further criticism of the state’s youth justice system.

Shadow Minister for Families and Children Georgie Crozier described the system as a ‘shambles’ on Saturday morning, sharing her thoughts via social media platform Twitter.

“Under [Premier] Daniel Andrews violence in youth justice is ongoing, whilst serious offenders are put into low security,” she tweeted.