One claimant who had several stints at Ashley Youth Detention Centre from 2002-07 says he was choked unconscious by a guard and woke to being raped.
He alleges the guard then said it won't be as painful next time because he was no longer a virgin.
He also alleges he was strip searched upon arrival and was one night told to perform a sex act on a guard who said there was "no use" yelling because he was the only person on duty.
It is claimed he was put in a headlock and abused with a prison key and that guards would watch him while he showered.
The four people, who were aged between 13 and 17 at the time of the alleged abuse, have lodged separate claims in the Supreme Court of Tasmania in Hobart.Â
They are being represented by Arnold Thomas & Becker, which has previously launched legal action against the Tasmanian government on behalf of three other former detainees.
Lawyer Joseph Ridley said he expected more claims would follow.
"These four cases are further shocking examples of the alleged abuse ... of children who were vulnerable and in the care of the state," he said.
A spokesman for the state government says it is unable to comment because legal action has been flagged.
After historical abuse allegations were made public, the state government in September announced the centre would close within three years and be replaced with two smaller facilities.
It has insisted all current detainees are safe.
The four claimants are seeking damages and some allege known abuse wasn't reported to police and there was a culture in which staff were permitted to abuse detainees without fear of repercussions.
According to documents filed with the court, a girl was sexually abused by a detention centre staff member two to three times a week in the mid-1990s.
She was also allegedly left in isolation for three to four days in a row and only let out for 30 minutes day.
One boy, who was at the detention centre in 1996, was allegedly pinned down in a room and raped by a guard.
Another boy who was at the centre for several months in 2000 was allegedly placed in a room without surveillance cameras known as "the boob".
It is claimed he was punched and kicked by guards, had water poured on his head and was given a bucket to use as a bathroom.
He was allegedly sexually abused on one occasion by a guard under the false pretence of a contraband check.
A commission of inquiry examining child sexual abuse in Tasmania's public institutions will in August hold hearings specifically in relation to the detention centre.
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