U.S. Secretary of State John Kerry on Thursday declared that violence by ISIS against religious minorities was genocide, saying the United States would do everything it could to hold the militant group accountable.

"In my judgment Daesh [ISIS] is responsible for genocide against groups ... under its control, including Yazidis, Christians and Shia [Shi'ite] Muslims," Kerry said in a statement to reporters.

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"Naming these crimes is important, but what is essential is to stop them," Kerry said.