Dozens of Alice Springs prison guards have walked off the job over the Northern Territory government's public sector pay freeze.
The protected 12-hour strike on Thursday is also protesting the alleged under-resourcing of the sector, with the union saying it is in crisis.
Wage negotiations started in mid-2021 with workers demanding a three or more per cent annual pay rise to keep pace with cost-of-living increases.
The Gunner government has refused to accept the deal or address chronic short staffing, United Workers Union NT says.
"Alice Springs has not been properly staffed for over 30 years, since it first opened," UWU NT secretary Erina Early told AAP.
He said they were always 50 to 60 corrections officers down a day.
"They are exhausted and they feel the government is not respecting the risk they face every day."
About 60 officers have taken industrial action.
NT Correctional Services has previously said it had contingency plans in place to ensure the security and safety of prisoners, workers and the community.
"Functions, including the delivery of meals, the administering of medication and attending to the medical needs of prisoners will continue," a spokesman said.
The Alice Springs Correctional Centre is a minimum to maximum-security prison for men and women. It has a capacity of about 650 prisoners and is currently holding 633.
The NT government introduced a four-year pay freeze for more than 20,000 public servants in November 2020 in a bid to save over $400 million amid ongoing deficits and climbing debt levels.
It was accepted by 57 per cent of employees.
About 60 officers from the Darwin correctional centre walked off the job on Monday.
The annual inflation rate in Australia surged to 5.1 per cent in the March quarter, according to the Australian Bureau of Statistics.