SPRINGFIELD, Ill. (AP) — Illinois officials are cutting costs by putting violent prisoners in less-secure prisons, a driver behind a 51 percent increase in inmate assaults over two years, a state employee union said Thursday.

The American Federation of State, County and Municipal Employees Council 31 asserted that Gov. Bruce Rauner's campaign to reduce the prison population has meant an 18 percent drop in maximum-security prison populations.

At the same time, assaults on corrections officers jumped from 541 in 2015 to a projected 819 this year, AFSCME Executive Director Roberta Lynch, surround...