Twenty-one people have been charged after a riot at a juvenile justice centre on the NSW Central Coast that lasted for more than 20 hours.

The riot broke out at Frank Baxter Juvenile Justice Centre at Kariong about 8.30pm on Sunday, with allegations several inmates assaulted each other and then climbed onto the roof of the complex.

Seven were injured and six were taken to hospital, including an 18-year-old who was in a critical condition with stab wounds and facial injuries.

Three men are being treated at Gosford Hospital, including one with stab wounds and a collapsed lung, another with head and face injuries and a third with a broken ankle.

Nine detainees surrendered on Monday before riot squad officers moved on to the roof about 5.30pm – 21 hours after the riot started. The remaining 11 detainees surrendered peacefully, NSW Police said.

Five adults and 16 teenagers have been charged with riot.

One of the adults faced Gosford Local Court on Monday and the remaining four are due to appear at the same court on Tuesday.

The 16 youths are expected to appear in Woy Woy Children’s Court on Tuesday.

NSW Families, Communities and Disability Services Minister Gareth Ward said the incident was unacceptable and asked for an urgent independent review.

It will be conducted by former assistant police commissioner Lee Shearer and is in addition to plans already in place to establish a unit at the complex to manage high-risk offenders, he added.

“This inquiry will get to the bottom of what happened at Frank Baxter,” Mr Ward said on Monday.

“While the incident will be subject to a police investigation, actions that put the safety and security of staff and detainees at risk will not be tolerated.”

Public Service Association general secretary Stewart Little alleged the group targeted sex offenders within the complex and described the riot as “nothing short of horrific”.

He called for a judicial inquiry into the juvenile system, noting it’s not the first riot at the centre.

-AAP