Obama on Iraq: US cannot look away

US President Barack Obama has said that the US must not "look away" as Islamic State (IS) militants advance in northern Iraq, threatening religious minority groups.

Thousands of refugees from the Yazidi religious minority have fled their homes in recent days and are stranded in the Sinjar mountains, hiding from the jihadist fighters.

The US has conducted its second air-drop of food and water to those affected, hours after Washington launched fresh air strikes against the militants.