Kurdish "peshmerga" troops stand guard during an intensive security deployment at the checkpoint at the entrance to Sulaimaniya province August 8, 2014. Photo: Reuters
The US says it has launched an air strike against militants from the Islamic State (IS) group in Iraq.
The Pentagon said American aircraft attacked artillery that was being used against Kurdish forces defending the northern city of Irbil.
President Barack Obama authorised air strikes on Thursday, but said he would not send US troops back to Iraq.
US President Barack Obama talks about the humanitarian relief situation in Iraq, at the State Dining Room of the White House in Washington August 7, 2014. Photo: Reuters
The Sunni Muslim group IS, formerly known as Isis, now has control of large swathes of Iraq and Syria.
In June, IS took control of the city of Mosul. Earlier this week, its fighters seized Qaraqosh, Iraq's biggest Christian town, and other towns nearby.
'CAREFULLY AND RESPONSIBLY'
According to the Pentagon statement, two F/A-18 aircraft dropped 500-pound laser-guided bombs on mobile artillery near Irbil.
Pentagon press secretary Rear Admiral John Kirby said IS had been using the artillery to shell Kurdish forces defending Irbil, where US personnel are based.
Struggle for Iraq: In maps
Speaking on Thursday, Obama said the Iraqi government had requested assistance and the US would act "carefully and responsibly, to prevent a potential act of genocide" against the Yazidi and Christian communities - both minority groups in Iraq.
Islamic State fighters have taken control of large parts of northern Iraq since launching an offensive in June. Photo: Reuters
Dr Marzio Babille, Unicef's representative in Iraq, said the Yazidis were in an extremely precarious situation because of the "very aggressive and brutal" IS militants.
He said there were many "logistical and strategic difficulties", but added that a humanitarian corridor needed to be established.