Two men have been charged over an alleged plot to kill two South Australian judges and destroy their homes.
Police say the men also planned to burn down the home of a senior police officer.
A 63-year-old man from Murray Bridge allegedly offered to pay a 44-year-old man to carry out the crimes as retribution.
Detective Inspector Greg Hutchins says police believe the attacks were imminent, and potentially would have been carried out this week.
He says the arrests were made on Sunday after a six-week investigation.
'This was a planned attack on two state institutions – the police and the judiciary," he said in a statement.
"There's no doubt that this operation thwarted a plan that could have easily ended in multiple deaths and significant loss of property."
The men will face court on Monday charged with conspiracy to murder and conspiracy to commit arson on a home thereby endangering life.
Detective Inspector Hutchins says the safety of those being targeted, and that of their families, was the highest priority during the investigation.
"There's no doubt this was a very stressful situation for them and they have managed it with absolute professionalism," he said.
"Following today's arrests police will continue to monitor for any ongoing risk."
He says the investigation is continuing in respect to possibly identifying others who may have assisted.