Washington, June 12 (RHC)-- A coalition of immigration and civil rights groups has filed a complaint alleging "widespread and systematic" abuse of migrant children by U.S. Customs and Border Protection.

Organizations including the National Immigrant Justice Center and the ACLU, the American Civil Liberties Union, say they’re acting on behalf of over 100 unaccompanied children mistreated by border agents after crossing into the United States.

According to the groups, the vast majority of children were fleeing violence in their home countries. The alleged mistreatment has taken on new urgency with a recent surge of unaccompanied migrant children held in U.S. custody.

Over 1,000 children are reportedly being detained at a single warehouse in Arizona in substandard conditions.