Air strikes conducted near Erbil and the Mosul dam amid reports of mass killings by Sunni fighters in Syria.
The United States has conducted air strikes in Iraq against the Islamic State goup amid reports of more atrocities carried out by its fighters in neighbouring Syria.
Air strikes on Saturday targeted Islamic State fighters near the Kurdish capital of Erbil and the Mosul dam.
"The nine air strikes conducted thus far destroyed or damaged four armoured personnel carriers, seven armed vehicles, two Humvees and an armoured vehicle," the US Central Command said in a statement.
The Central Command said the strikes were aimed at supporting humanitarian efforts in Iraq and protecting US personnel and facilities there.
The Mosul dam, Iraq's biggest, fell under control of Islamic State fighters earlier this month. Control of the dam could give the Sunni fighters the ability to flood cities and cut off vital water and electricity supplies.
After the Islamic State's capture of the northern city of Mosul in June, its swift push to the borders of Iraqi Kurdistan alarmed Baghdad and last week drew the first US air strikes on Iraq since the withdrawal of US troops in 2011.
Iraq has been plunged into its worst violence since the peak of sectarian bloodshed in 2006-2007, with Sunni fighters led by the Islamic State overrunning large parts of the west and north, forcing hundreds of thousands to flee for their lives and threatening ethnic Kurds in their autonomous province.
The Islamic State has also seized large parts of Syria as it tries to build a caliphate across several countries.
On Saturday, the Syrian Observatory for Human Rights said Islamic State fighters had killed about 700 members of a tribe in eastern Syria.
The monitoring group said the killings took place in several villages inhabitated by the al-Sheitat tribe in Deir Ezzor province. The Observatory said many of the victims were beheaded after being captured.