SEOUL, South Korea (AP) — A human rights group says it has identified hundreds of sites where witnesses claim North Korea has carried out public executions as it continues to arbitrarily and aggressively use the death penalty to intimidate its citizens.

The Seoul-based Transitional Justice Working Group said Tuesday its research was based on more than 600 interviews with North Korean defectors who helped locate the sites with satellite imagery. It didn't reveal the exact locations of the 323 sites out of concern that North Korea would tamper with them.

The report says North Korean executions tend to occur at riverbanks, hills and at marketplaces and school grounds, and that residents and family members of those sentenced are often forced to attend the killings, conducted mostly by firing squads.