U.S. says conducts air strikes in Iraq near Arbil and Mosul dam

The Mosul dam, Iraq's biggest, fell under control of Islamic State militants earlier this month. Control of the dam could give the Sunni Islamists 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 U.S. air strikes on Iraq since the withdrawal of U.S. troops in 2011.

"The nine air strikes conducted thus far destroyed or damaged four armored personnel carriers, seven armed vehicles, two Humvees and an armored vehicle," the U.S. Central Command said in a statement.

It said the strikes were conducted with a mix of fighters and drones, adding: "All aircraft exited the strike areas safely."

The Central Command said the strikes were aimed at supporting humanitarian efforts in Iraq and protecting U.S. personnel and facilities there.

Iraq has been plunged into its worst violence since the peak of a sectarian civil war 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 national borders drawn up by European a century ago.

Following the announcement this week by Iraqi Prime Minister Nuri al-Maliki that he would step aside after eight years in power, U.S. officials have said Washington may accelerate U.S. economic and military aid to Iraq if the new leadership is more inclusive.