Military officials said they destroyed armoured carriers and a truck, in what was the third round of air strikes since they were authorised by the President on Thursday.
Until then the U.S. had not carried out its own official military operations in Iraq since the withdrawal in late 2011.
It returned to battle on Friday when two F/A-18 jets dropped 500lb bombs on Islamic State fighters advancing on the Kurdish capital of Irbil as violence sent the number of displaced Iraqis soaring.
And while Mr Obama admitted the U.S. military cannot bring peace to Iraq, he said the air strikes were "part of a long-term project" that will continue until Iraq can form a government capable of ensuring the security of its borders.
"We can conduct air strikes, but ultimately there's not going to be an American military solution to this problem," he said. "There's going to have to be an Iraqi solution that America and other countries and allies support."
