They are falling ill by the hundreds in the remote desert camp where they are confined.
Hundreds may still be living with the militants — and in some cases have grown to love them.
Even after the defeat of its so-called caliphate, the Islamic State still wreaks havoc.
The eight, including two women, were among around 13,000 foreigners being held by U.S.-allied Kurds in Syria.
Tehran is seeking to exact a cost for U.S. sanctions that have battered its economy, but it wants to avoid all-out war.
Spending cutbacks by the Iran-allied Lebanese militia illustrate the profound impact of the sanctions, which are curtailing Iran’s ability to support its most powerful regional proxy.
The president said it “may very well be a good thing” to confuse Iran about U.S. intentions.
The unplanned visit comes as some European diplomats fear new conflict between Iran and the United States.
Alleged attacks follow U.S. warnings that Iran might target commercial shipping in the area, although Saudi Arabia did not say who was responsible.
The U.S., Russia, Iran, Syria and a host of proxy forces are in a high-stakes race to seize territory.