The union representing prison guards says claims restrained youths were punched and kicked by guards at an adult Melbourne prison are "lies".
A lawyer acting for teenage boys allegedly involved in Monday night's riot at the youth unit of the Barwon maximum security adult prison said that they were subjected to systematic violence.
"Children are telling me they were pinned to the floor by guards from the adult section of the prison and kicked and punched in the head," Alina Leikin from the Human Rights Law Centre said on Friday.
"Numerous boys have visible injuries including bruising and one boy was hospitalised with a head injury requiring stitches."
The Community and Public Sector Union said the HRLC's claims are headline grabbing hyperbole.
"I'm not sure why the HRLC would be proffering lies and innuendos," CPSU spokesman Julian Kennelly told AAP on Friday.
The union says a senior officer was punched by a boy who said for weeks "he would bring one of these officers down".
The officer suffered a fractured skull, cheek and eye socket and will be off work for some time, according to the union.
After an initial fight, 16 young offenders barricaded themselves in an exercise yard and then broke into the visitors' centre before reinforcements from Corrections used capsicum spray to subdue them.
The HRLC says the spray was used indiscriminately in the confined space by a number of prison officers and boys who weren't involved in any disturbance were sprayed "directly and deliberately".
But the union says the tactics used were no different than police would use to quell fighting on the streets.
Numerous boys reported they were assaulted while restrained with punches to the face and head and kicks to the ribs, back and head, the HRLC says.
Guards also allegedly said: "Next time I'll break you". The union denied these accusations.
A spokesman for Department of Justice and Regulation said they will not comment on the matter as it is now being investigated by police.
"Allegations against staff relating to the incident at the Grevillea unit on Monday night (13 February) have been referred to Victoria Police, as is standard practice," he said.
Victoria's Youth Affairs Minister Jenny Mikakos said the relevant departments are fully cooperating with the police investigation.
Corrections Minister Gayle Tierney has been contacted by AAP for comment.