Six U.S. troops in Syria suffered traumatic brain injuries during two different attacks last week by Iran-backed militants, the Pentagon said on Thursday, adding they were diagnosed during routine screenings in recent days.

The disclosure further raises the human toll among American forces from strikes and counter-strikes last week, which killed on American contractor, injured another and wounded six U.S. troops.

The Pentagon also estimated eight militants were killed during retaliatory U.S. air strikes against two Iran-linked facilities in Syria.