UN human rights chief Navi Pillay on Monday condemned the Islamic State jihadists for their campaign of "ethnic and religious cleansing" in Iraq.

"They are systematically targeting men, women and children based on their ethnic, religious or sectarian affiliation and are ruthlessly carrying out widespread ethnic and religious cleansing in the areas under their control," Pillay said in a statement.

"Such persecution would amount to crimes against humanity," she added.