"The secretary-general urges the international community to unite in showing solidarity with Iraq as it confronts this serious security challenge," his spokesman said in a statement yesterday.
The UN chief demanded "full respect for international humanitarian law and human rights law in efforts to counter terrorism and violence in Iraq," spokesman Stephane Dujarric added.
Ban strongly condemned the surge in violence and warned that "terrorism must not be allowed to succeed in undoing the path toward democracy in Iraq."
The speed with which ISIL and its allies have advanced after their seizure on Tuesday of Mosul -- a city of two million people -- has sent alarm bells ringing in Western capitals.