At least four hostages held by the Islamic State group in Syria, including the murdered American journalist James Foley, were "waterboarded" in the early part of their captivity, a US newspaper has reported.
The Washington Post on Thursday quoted sources as saying that Foley and other kidnapped Westerners were subjected to the simulated drowning torture "several times" by people who "knew exactly how it was done".
The AFP news agency quoted its own source as saying that at least one hostage had been waterboarded.
Waterboarding was used by the CIA during interrogations of those it suspected of terrorism during the so-called "war-on-terror" era of president George W Bush.
It used on Khalid Sheikh Mohammed, an al-Qaeda operative the US said was closely involved with the planning of the attacks of September 11, 2001 and other high-profile operations.
The US abandoned the technique after the election of Barack Obama, and following revelations that it gained the US no usable intelligence, and legal opinions ruled it "cruel and unusual punishment".
The captives, including Foley who was kidnapped in northern Syria in November 2012, were held in Raqqa, the Syrian capital of the Islamic State group.
The Islamic State last week released a video of the murder of Foley. A masked fighter who appeared in the video said the journalist's killing was a response to US air attacks against the Islamic State group in Iraq.