High-security prisons across California have tightly restricted movement, calls and visits while officials probe a surge in violence this year. The restrictions started Saturday and affect the top-security sections of nearly a dozen lockups including the California Correctional Institution,

The day before state authorities announced plans to restrict inmate movement and revoke visits and other privileges, three inmates were killed in attacks at three different prisons.

The California State Prison, Sacramento is among facilities that are being placed on modified movement after a surge in violence, correctional officers said.