US bombs Islamic State

Barack Obama authorised the first US air strikes on Iraq since he pulled all troops out in 2011.

FILE: A popular committee fighter supporting Iraqi government forces campaign against jihadist militants from the Islamic State (IS) guards a position in the town of Taza Khurmatu as fighting on the front line continued on 8 August 2014. Picture: AFP.

BAGHDAD - US fighter jets and drones have repeatedly bombed Sunni extremists in northern Iraq targeting Isis artillery units and convoys advancing on the Kurdish regional capital, Irbil.

The airstrikes ramped up America's involvement in Iraq where the Isis movement has been seizing control of towns and key infrastructure in an advance that has forced hundreds of thousands to flee.

Islamic State fighters, who have beheaded and crucified captives in their drive to eradicate unbelievers, have advanced to within a half hour's drive of Arbil, capital of Iraq's Kurdish region and a hub for US oil companies.

They have also seized control of Iraq's biggest dam, Kurdish authorities confirmed on Friday, which could allow them to flood cities and cut off vital water and electricity supplies.

The Pentagon said two F/A-18 aircraft from an aircraft carrier in the Gulf had dropped laser-guided 500-pound bombs on the fighters' artillery and other air strikes had targeted mortar positions and an Islamic State convoy.

US President Barack Obama authorised the first US air strikes on Iraq since he pulled all troops out in 2011, arguing action was needed to halt the Islamist advance, protect Americans and safeguard hundreds of thousands of Christians and members of other religious minorities who have fled for their lives.

For the second straight night, the United States also dropped relief supplies to members of the ancient Yazidi sect, tens of thousands of whom are massed on a desert mountaintop seeking shelter from fighters who had ordered them to convert or die.

"Earlier this week, one Iraqi in the area cried to the world, 'There is no one coming to help'." Obama said.

The Islamic State was defiant. A fighter told Reuters by telephone the US air strikes would have "no impact on us".

"The planes attack positions they think are strategic, but this is not how we operate. We are trained for guerrilla street war," he said. "God is with us and our promise is heaven. When we are promised heaven, do you think death will stop us?"

The advance of the Sunni militants, who also control a third of Syria and have fought this past week in Lebanon, has sounded alarm across the Middle East and threatens to unravel Iraq, a country divided between Shi'ites, Sunnis and Kurds.

In Baghdad, where politicians have been paralysed by infighting while the state falls apart, the top Shi'ite cleric all but demanded Prime Minister Nuri al-Maliki quit, a bold intervention that could bring the veteran ruler down.