Secretary-General Ban Ki-moon is urging the world's nations to respond to violent extremism with "cool heads and common sense," not with "mindless policies" that turn people against each other, alienate marginalized groups and play into the hands of the enemy.

The U.N. chief told the General Assembly on Friday that his new plan to prevent violent extremism is an urgent call to all 193 U.N. member states to address the causes of violent extremism, listen to people's grievances and ensure that human rights and due process aren't trampled.

Ban says governments must never forget that "terrorist groups are not just seeking to unleash violent action, but to provoke a harsh reaction."

He asks countries to create national plans to counter the rapid expansion of violent extremist ideologies online and elsewhere.