WASHINGTON, Jan. 8 (Xinhua) -- U.S. Secretary of Defense Mark Esper said Wednesday that Iran launched 16 short-range ballistic missiles from three locations within Iran in Tuesday's attack.

Esper, with Chairman of the U.S. Joint Chiefs of Staff Mark Milley aside, told reporters that, among the 16 missiles, 11 hit the Ayn al-Asad air base and at least one landed at a base near Erbil, adding that the missiles damaged tents, taxiways, parking lots and a helicopter.

Milley said Iran's missiles were aimed at facilities and personnel at the two bases in Iraq.

"I believe, based on what I saw and what I know, that they were intended to cause structural damage, destroy vehicles and aircraft, and to kill personnel," he noted, pointing out that defensive techniques of U.S. forces helped to keep the damage at a limited level.

In his address to the nation earlier in the day, U.S. President Donald Trump attributed the absence of casualties to the precaution measures, dispersal of forces, and effective early warning system.

The Pentagon Tuesday confirmed Iran's launching of more than a dozen ballistic missiles against at least two military bases housing the U.S. and coalition forces in Iraq.

Iran's Islamic Revolution Guard Corps claimed responsibility for the missile attacks, saying that they were meant to retaliate against the U.S. killing of General Qassem Soleimani.