Washington, Jan 22 (AP) President Donald Trump on Wednesday minimised the severity of head injuries sustained by US troops during an Iranian missile strike on an Iraqi air base as he was pressed on why he'd claimed no troops had been injured in the attack.

"I heard they had headaches and a couple of other things...and I can report it is not very serious," Trump said at a press conference in Davos, Switzerland, arguing that potential traumatic brain injuries are less severe than, say, missing limbs.

"No, I don't consider them very serious injuries relative to other injuries that I've seen," the Republican president said.

"I've seen what Iran has done with their roadside bombs to our troops. I've seen people with no legs and with no arms. I've seen people that were horribly, horribly injured in that area, that war. No, I do not consider that to be bad injuries, no," he said.

In addition to the 11 service members who were flown out of Iraq on January 10 and January 15 for further examination of concussion-like symptoms, defence officials said that about 10 more were flown to Germany in recent days.

Most were being treated for symptoms related to possible traumatic brain injury; a smaller number may have been suffering from psychological trauma, according to two defense officials who discussed the matter on condition of anonymity.

The exact nature and severity of the apparent brain injuries has not been publicly released.

Trump has repeatedly claimed that no Americans were harmed in the Iranian missile strikes on January 8, which came in retaliation for a US drone strike that killed Qassem Soleimani, Iran's most powerful military general.

The question of American casualties was especially significant at the time because Trump cited the fact that no Americans were killed or inured as driving his decision not to retaliate further and risk a broader war with Iran.

But in the days following the attack, medical screening determined that some of the US troops who took cover during the attack were suffering from concussion-like symptoms.

Last week, 11 US service members were flown from Iraq to US medical facilities in Germany and Kuwait for further evaluation of concussion-like symptoms.

This was not reported to Defense Secretary Mark Esper until the day it was publicly announced, last Thursday; this comports with the usual practice of not reporting injuries to the Pentagon unless they involve the loss of life, limb or eyesight.

Trump told reporters he was informed of the concussion issue "numerous days" after the attack.

US Central Command, which oversees military operations in the Middle East, said in a statement Tuesday evening that given the nature of the reported injuries, "it is possible additional injuries may be identified in the future." (AP)

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