Corrections officers at dozens of prisons have walked off the job in response to an alleged violent assault on a colleague.
Staff at 30 prisons across NSW have gone on strike after a prisoner accused of assaulting an officer was released from custody on Monday.
Prisoners were locked in their cells and trucks transporting prisoners to court returned inmates after officers walked out on Tuesday morning.
Court matters requiring prisoners to appear via audiovisual link were also affected.
The alleged assault occurred on July 25, when an officer was bashed at the John Morony Correctional Centre, near Windsor in Sydney's northwest.
A union representing prison officers said the man sustained broken ribs, lost teeth, and received a broken nose and eye socket.
Public Service Association general secretary Stewart Little condemned the officer's bashing.
"He has assaulted the officer while the officer was trying to help him, trying to set up (a call) so this guy could speak to his family ... unprovoked, cowardly attack," he told AAP.
On Tuesday morning, police arrested a 21-year-old man in Blacktown, in western Sydney, and charged him causing grievous bodily harm to a law enforcement officer.
The man did not apply for bail in the Blacktown Local Court. He will next appear in court on October 16.
Mr Little blamed crowded jails as a result of a government crackdown on domestic violence, and staff shortages, for creating a volatile NSW prison system.
"Corrections officers need to be backed up by the rest of the justice system and the government otherwise this strike will only be the beginning," he said.
Staff are expected to return to work at 7am on Wednesday.
Corrective Services NSW said the matter had been referred to the Industrial Relations Commission.
"Staff are right to expect that inmates who assault them in the workplace will be met with the full force of the law and we encourage staff on duty to remain at work whilst police investigate," a spokeswoman said.
"CSNSW is continuing to support the injured officer who, like all staff, deserves to be safe at work."
It is the second strike in less than a year, following a mass walkout in October in response to the sentence given to a man responsible for assaulting four guards at Cessnock Correctional Complex.
Cameron Welsh was initially issued with a three-year community corrections order after being convicted of four counts of assaulting a law enforcement officer and one count of intimidating with the intent to cause fear or physical harm.
But an appeal judge, who called the initial sentence an affront to justice, gave Welsh an extra two years and nine months in prison.
Australian Associated Press