The comments by Randall Schriver, who leads Asia policy at the U.S. Defense Department, are likely to increase tension with Beijing, which is sensitive to international criticism and describes the sites as vocational education training centers aimed at stemming the threat of Islamic extremism.
Former detainees have described to Reuters being tortured during interrogation at the camps, living in crowded cells and being subjected to a brutal daily regimen of party indoctrination that drove some people to suicide.
Some of the sprawling facilities are ringed with razor wire and watch towers.
“The (Chinese) Communist Party is using the security forces for mass imprisonment of Chinese Muslims in concentration camps,” Schriver told a Pentagon briefing during a broader discussion about China’s military, estimating that the number of detained Muslims could be “closer to 3 million citizens.”