Thousands of mental health workers at Kaiser Permanente facilities spanning across Southern California went on strike on Monday, calling for increased pay and restored pension plans, amid other demands.

The National Union of Healthcare Workers said nearly 2,400 mental health workers launched the job action after Kaiser Permanente management turned down their proposals.

The union that represents nearly 2,400 mental health care workers in Southern California — 316 in San Diego County — filed a strike notice with Kaiser Permanente on Friday, putting their employer on notice that they intend to launch an “indefinite” strike starting on Oct. 21.